Psychology
2013. Vol.4, No.11A, 4-10
Published Online November 2013 in SciRes (http://www.scirp.org/journal/psych) http://dx.doi.org/10.4236/psych.2013.411A002
Open Access 4
Explicit and Implicit Memory in Depressive Patients.
Review of the Literature
Chrystel Besche-Richard1,2
1Laboratoire Cognitio n , Santé, Socialisation, C2 S EA 6291, Université de Reims Champ agne-Ardenne,
Reims, France
2Institut Universitaire de France, Paris, France
Received August 25th, 2013; revised September 27th, 2013; accepted October 23rd, 2013
Copyright © 2013 Chrystel Besche-Richard. This is an open access article distributed under the Creative Com-
mons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, pro-
vided the original work is proper ly cited.
The cognitive approach to depressive disorders has generally focused on memory problems. In recent
years, research conducted in this field has been based on new cognitive theories of memory that distin-
guish between implicit memory, i.e. an unconscious memory that promotes the use of automatic processes,
and explicit memory, i.e. a conscious memory based on the use of controlled processes. Here, we propose
a review of the literature concerning the studies of depressive pathology. The initial results suggested a
specific impairment of the explicit memory and thus brought depressive pathology into the realm of the
pathologies of consciousness. More recent results and/or a consideration of divergent findings have led
researchers to revise this interpretation. After looking at the various studies, we shall point out certain di-
vergent results that will allow us to propose some new explanations and, finally, some new avenues of
research based on the consideration of clinical and methodological elements. This approach is based on a
cognitive and clinical examination of depressive disease. We examine the role of the processes—data—or
conceptually driven processes, the role of the paradigm used, and clinical profile with a special interest
for the presence of anxious or psychotic symptoms, and for the emotional profile.
Keywords: Depression; Implicit Memory; Explicit Memory; Recognition; Recall; Cognition
Introduction
Depression is characterized by a constellation of behavioral,
emotional, and cognitive symptoms especially in the domain of
memory (Gotlib & Joormann, 2010; Schaub et al., 2013). Mem-
ory disorders in major depressive episodes have attracted much
interest with the development of new cognitive models that
distinguish between implicit and explicit measures of memory.
These two types of memory, initially revealed through the study
of amnesic patients, correspond to an unconscious and auto-
matic form of memory (implicit memory) and a conscious,
strategy form that requires the intervention of controlled proc-
esses (explici t memory).
What is the likely value of conducting a review of the litera-
ture on implicit and explicit memory functioning in the field of
depressive pathology? This exercise is underpinned by a num-
ber of theoretical, methodological and clinical reasons. In effect,
even though the results reported to date support a number of
robust hypotheses, certain divergent results that primarily relate
to the functioning of implicit memory in these patients still
need to be accounted for. Furthermore, we consider that the
recent methodological advances achieved in the exploration of
the implicit and explicit forms of memory in normal individuals
will also make it possible to advance our understanding of de-
pressed patients.
This article therefore consists of three sections: firstly, we
shall review the published studies that deal with implicit and
explicit memory functioning in depressed patients; secondly,
we shall present the reasons thought to account for certain di-
vergent results; finally, we shall make a number of propositions
that we believe will allow us to advance our understanding of
memory impairments in depressed patients and their links with
the clinical description of depression.
Is Depression a Pathology of Consciousness?
The impairment of memory functions was pointed out in
clinical descriptions of depressive disorders at a very early
stage. The first studies, conducted as of the 1970s (Calev &
Erwin, 1985; Calev, Korin, Shapira, Kugelmass, & Lerer, 1986;
Cohen, Weingartner, Smallberg, Pickar, & Murphy, 1982;
Dunbar & Lishman, 1984; Golinkoff & Sweeney, 1989; Hart-
lage, Alloy, Vasquez, & Dykman, 1993; Henry, Weingartner, &
Murphy, 1973; Johnson & Magaro, 1987; Roy-Byrne, Wein-
gartner, Bierer, Thompson, & Post, 1986; Sternberg & Jarvik,
1976; Stromgren, 1977; Weingartner, Cohen, Murphy, Martello,
& Gerdt, 1981), focused on exploring the explicit functioning
of memory in depressed patients and indicate the difficulties
encountered by these patients when presented with traditional
memory tasks. The differences between depressed patients and
control participants seem to be greater in free recall than in
cued recall tasks (Cohen et al., 1982). Furthermore, recall is
poorer in depressed patients when they are required to develop
elaborate strategies during the encoding phase. According to
the authors, these results suggest a deficit in the spontaneous
use of certain encoding strategies (Channon, Bake r, & Roberton,

C. BESCHE-RICHARD
1993; Watts, Dalgleish, Bourke, & Healy, 1990; Weingartner et
al., 1981) which may nevertheless be effectively mobilized in
other situations (Hertel & Rude, 1991). However, not all the
explicit memory tasks have resulted in the observation of im-
pairments in depressed patients: no systematic difference be-
tween the performances of depressed patients and control par-
ticipants have been observed in recognition tasks (Calev &
Erwin, 1985; Dunbar & Lishman, 1984; Golinkoff & Sweeney,
1989; Miller & Lewis, 1977), with performances generally
being more impaired when recall is delayed (Ellwart, Rink, &
Becker, 2003). These results have been confirmed by more
recent studies as one of Fossati et al. (2004) who showed an
impairment of free recall contrary to preserved cued recall and
recognition in major depressive patients.
The 1990s saw the first investigations of implicit memory in
connection with depression, resulting in studies that compared
implicit and explicit memory performances in this clinical
population. We shall therefore present the results of studies
published between 1990 and 2013 that have investigated the
operation of implicit and explicit memory in relation with
thymic disorders. The first study was conducted by Hertel and
Hardin (1990) who compared memory performances in a
homophone spelling task and a recognition task. This initial
study was not conducted using a clinical population of patients
meeting the current diagnostic criteria for a major depressive
episode but, instead, among students who were asked to com-
plete a self-questionnaire for the evaluation of depression fol-
lowing the induction of a depressive or neutral mood. The re-
sults reveal dissociation between the performances as a function
of the implicit or explicit nature of the tasks used. In effect, the
performances of the two participant groups did not differ on the
homophone spelling task (implicit task), unlike in the recogni-
tion task (explicit task). This dissociation has been confirmed
by the results of a number of other studies (Bazin, Perruchet,
De Bonis, & Féline, 1994; Beato & Fernández, 1995; Danion,
Willard-Schroeder, Zimmermann, Grangé, Schlienger, & Singer,
1991; Jenkins & McDowall, 2001). Unlike Hertel and Hardin’s
work (1990), these studies have generally called upon groups of
depressed patients, hospitalized and recruited in accordance
with standardized diagnostic criteria. The patients who took
part on these studies were severely depressed at the time of
their inclusion, as the high scores they obtained in the em-
ployed clinical e v aluation scales tes ti fy (see Table 1).
Only one study has reported divergent results: this is the
study conducted in 1992 by Elliott and Greene that made use of
a set of four memory tasks consisting of two implicit tasks
(completion of trigrams, homophone spelling) and two explicit
tasks (free recall and cued recall). The patients exhibited more
severe memory disorders than those found in the other studies
because their performances were impaired in the explicit as
well as the implicit tasks. This result may first of all be ex-
plained by the contamination phenomena related to the sub-
jects’ use of explicit retrieval strategies during implicit recovery.
If this is the case, then the implicit memory impairments re-
vealed in the depressed patients may be explained by their
poorer use of these strategies in the employed tasks. In their
review of the literature on implicit memory functioning in de-
pressed patients, Roediger and McDermott (1992) discuss this
result at length and propose a number of interpretations. First of
all, these authors point out a methodological bias that relates to
the evaluation of the baseline for the stimuli that were not stud-
ied since Elliott and Greene (1992) did not use the traditional
procedure which consists of counterbalancing the studied ver-
sus non-studied items in the experimental design but, instead,
used normative data from the literature in order to evaluate this
baseline. This methodological specificity might therefore go
some way to explaining the performances observed in the de-
pressed patients on the implicit tasks. Finally, Roediger and
McDermott refer to the nature of the cognitive processes mobi-
lized by the task—data-driven or conceptually-driven processes
Table 1.
Characteristics of the studied population and mean sco res in the clinical scales obtained by the participants in the various cited studies.
Studied population Mean scores in the clinical scales
Bazin et al., 1994 23 depressed patients, 37 control subjects matched for gender, age and academ ic levelMADRS: 35.26; BDI: 21.3
Beato & Fernández, 1995 24 depressed subjects, 24 control subjects doubtlessly
not matched on age (35.1 vs. 27.7) and gender BDI: 23 (for the controls: 3.46)
Danion et al., 1991 18 depressed patients, 18 control subjects matched for gender, age and academ ic levelHDRS: 29.6
Elliott & Greene, 1992 10 depressed patients, 10 control subjects matched for gender, age and academic levelHDRS: 27.3
Hertel & Hardin, 1990
Experiments 1 & 2: 48 (experiment 1) and 34 (experiment 2) psychology students
whose score on the BDI was less than or equal to 6, followed
by the induction of a neutral or depressed mood.
Experiment 3: 91 psychology students divided into 3 groups: naturally depressed
(BDI > 9), induction of a neutral mood, - not depressed (BDI < 6),
induction of a neutral or depressed mood.
In experiments 1 & 2, there was no
significant difference on the BDI score
following the induction of a neutral or
depressed mood
Hertel & Milan, 1994 89 students evaluated using the BDI two weeks before their participation; Two groups: dysphoric (BDI > 9), non dysphoric (BDI < 7) evaluated again
with the BDI after completing the memory tasks and with the STAI
Dysphoric: 1) BDI: 17.1 to 17.7,
2) STAI state: 48.7 to 53.3,
3) STAI trait: 51.5 to 53.2.
Non dysphoric: 1) BDI: 3.2 to 4.9,
2) STAI state: 36.1 to 40.5,
3) STAI trait: 35.7 to 39.3.
Jenkins & McDowall, 2001 10 depressed patients,10 control subjects matched for age and academic level BDI: 25.4 (for the control: 2.1)
Mulligan, 2011 66 subclinically depressed patients and their 66 controls BDI: 16.3 (for the controls: 2)
Note: BDI: Beck Depression Inventory; HDRS: Hamilton Depression Rating Scale; MADRS: Montgomery and Asberg Depression Rating Scale; STAI: State—Trait
Anxiety Inventory.
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C. BESCHE-RICHARD
—as the source of the impairment of implicit performances in
the depressed patients.
In the light of all these results, it currently seems difficult to
accept the idea that depressive pathology results in conscious
memory impairments and could therefore be qualified as pa-
thology of consciousness. If the initial results suggest the exis-
tence of a specific impairment of explicit memory that takes the
form of a degradation of the conscious system (Bazin et al.,
1994; Danion et al., 1991; Hertel & Hardin, 1990; Hertel &
Milan, 1994), more recent data (Beato & Fernández, 1995;
Jenkins & McDowall, 2001), even if it does not completely
invalidate this conclusion, indicates that the impairment of
memory functioning in depressed patients may be more global
and also affect implicit performances. It would appear that the
opposition between implicit and explicit memory is not suffi-
cient to explain all the results observed in depressed patients. In
effect, the results obtained by Beato and Fernández (1995) &
Jenkins and McDowall (2001) provide arguments in favor of
the functional theories of memory. However, there are not as
yet sufficient results available in this field to allow us to hy-
pothesize that there is a specific impairment of the conceptu-
ally-driven processes in depressed patients (see Table 2). It
should nevertheless be remembered that Elliott and Greene
(1992) observed an impairment of implicit perceptual memory
in the depressed patients in their study. Furthermore, in order to
evaluate explicit memory these authors, like Bazin et al. (1994),
used a familiar cued recall task in order to mobilize the data-
driven processes rather than the conceptual processes but that,
despite this, the depressed patients continued to exhibit deficits.
Summary of the Results on Implicit and Explicit
Memory Functioning in Depressed Patients:
Limitations of the Studies
Overall, the studies indicate, in a fairly stable way, an im-
pairment of explicit memory in depressed patients. The results
obtained by Beato and Fernández (1995) & Jenkins and
McDowall (2001) emphasize the fact that the hypo-functioning
of implicit memory is probably due to the impairment and/or
underuse of the conceptual processes, i.e. mechanisms that are
primarily mobilized in explicit tasks. If we accept the conclu-
sions formulated by these authors, according to whom memory
tests that are based on conceptually-driven information proc-
essing should be more greatly affected by depressive pathology
than those that are based on data-driven processing, then the
dissociation of performances should take the form of a disso-
ciation between impaired conceptual processes and preserved
data-driven processes and not between implicit and explicit
memory performances. This would then mean that the data-
driven processes are preserved in depressed patients. The sum-
mary of the obtained results runs counter to this conclusion
since we have seen that performances in explicit perceptual
tasks are also impaired in depressed patients. Nevertheless, no
comparison of a perceptual and a conceptual form of explicit
memory has ever been undertaken in depressed patients (only
on dysphoric population by Elliott & Greene, 1992) within the
framework of one and the same study.
Even though the results concerning the explicit evaluation of
memory in depressed patients are relatively consistent, the key
area of divergence relates to the performances observed in free
recall and recognition tasks since anomalies have rarely been
identified in depressed patients in this latter type of task.
Even though they belong to the group of explicit tasks, rec-
ognition tasks differ from the recall tasks in terms of the proc-
esses that they mobilize. As early as the 1970s, Kintsch argued
that different cognitive processes are involved in recall and
recognition tasks. In a classic recall task, the subject first gen-
erates the candidate items that have previously been activated
and then seeks the candidate that was seen during the encoding
phase (generation-recognition model). In a recognition task,
Table 2.
Tasks Used and Type of Mobilized Processes in the Various Cited St u di es .
Studies Tasks used Type of task/type of mobilized process Results
Bazin et al ., 1994 1) Trigram completion
2) Cued recall 1) Implicit m emory/Data-driven 2) Explicit memory/Data-drive n D = C D < C
Beato & Fernández, 199 5 1) Word f ragment completion 2) Category production
3) Free recall
1) Implicit m emory/Data-driven
2) Implicit memory/Conce ptually-driven
3) Explicit memory/Conceptua lly-driven
D = C
D < C
D < C
Danion et al ., 1991 1) Trigram completion
2) Free recall 1) Implicit m emory/Data-driven 2) Explicit memory/Conceptua lly-driven D = C D < C
Elliott & Greene, 1992
1) Trigram completion
2) Homophone spelling
3) Cued recall
4) Free recall
1) Implicit m emory/Data-driven
2) Implicit m emory/Data-driven
3) Explicit memory/Data-drive n
4) Explicit memory/Conceptua lly-driven
Dys < C
Dys < C
Dys < C
Dys < C
Hertel& Hardin, 1990 1) Homophone spelling
2) Recognition 1) Implicit m emory/Data-driven 2) Explicit memory/Data-drive n Dys = C Dys < C
Hertel& Milan, 1994 Process Dissociation Procedure ( P DP)1) Recollec t ion (conce ptually-driven)
2) Familiarity (Data-driven) Dys < C Dys = C
Jenkins & McDowall, 2001 1) Category association 2) Word fragment completion
3) Free recall
1) Implicit memory/Conce ptually-driven
2) Implicit m emory/Data-driven
3) Explicit memory/Conceptua lly-driven
D < C
D = C
D < C
Mulligan, 2011 1) Category p roduction
2) Category cued-recall 1) Implicit memory/Conce ptually-driven 2) Explicit memory/Conceptua lly-driven Dys < C if test-aware Dys < C
Note: D: De pressed patients; C: Control participa nts; Dys: Dysphoric participa nts.
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C. BESCHE-RICHARD
this search phase is replaced by a faster mechanism that directly
identifies the words seen during the training phase. The data
provided by Johnston, Dark, and Jacoby (1985) indicates that
two processes are involved in recognition tasks: on the one
hand, a process based on a feeling of familiarity and, on the
other, an active search mechanism that results in a memory
effect. The latter process would only occur in recognition tasks
if the former were to prove to be inadequate (Mandler, 1980).
The search mechanism, which is an elaborated, integrative
process, would therefore be optional as far as recognition per-
formance is concerned and would depend on the conditions
obtaining in the situation in question. The results of studies of
the neuroanatomy of memory that have revealed the activation
of different areas of the brain as a function of the nature of the
administered task (Cabeza, Kapur, Craick, & McIntosh, 1997)
argue in favor of differences between recall and recognition
tasks. Furthermore, this study emphasizes the fact that recogni-
tion tasks are more perceptual than recall tasks. According to
certain authors, the selective deficit in recall performances ob-
served among depressed patients suggests an impairment of the
memory search and retrieval mechanisms (Fossati, Coyette,
Ergis, & Allilaire, 2002; Ilsley, Moffoot, & O’Carroll, 1995).
Let us turn now to the clinical factors that might have an im-
pact on the nature of depressed patients' memory performances
and whose role cannot be ignored in the interpretation of the
results. Only in very few studies, have cognitivo-clinical corre-
lations between implicit and explicit memory performance s and
certain clinical factors related either directly or indirectly to the
depressive syndrome been conducted. Only four studies have
addressed the respective roles of anxiety and depression in
memory performance. All of these studies were conducted us-
ing emotionally valenced material in order to evaluate the cog-
nitive processing performed by subjects with regard to words
with a positive, negative (inducing depression or anxiety) or
neutral affective valence. Three of these studies used a cate-
gorical, non-dimensional clinical approach that compared
groups of anxious patients with groups of depressed patients
(Bradley, Mogg, & Williams, 1994, 1995; Tarsia, Power, &
Sanavio, 2003). The results reveal that memorized information
is processed differently depending on the semantic context of
the words and, furthermore, the clinical characteristics of the
patients (preferential treatment of depression-inducing words in
the depressed patients and preferential treatment of the anxiety-
inducing words in the anxious patients). The results obtained by
Tarsia et al. (2003), when considered independently of the af-
fective valence of the material, demonstrate the cognitive dif-
ferences associated with the specific clinical profiles since, in
their anxious participants, the authors observed an increase in
the priming effect in the implicit task (impairment of the auto-
matic processes) and, in the depressed subjects, a fall-off in
recall performances (impairment of the controlled processes).
These results therefore suggest that specific emotional dimen-
sions can modify the processing of the information that is to be
memorized and does so as a function of the implicit or explicit
nature of the employed task. We can ask ourselves to what
extent the dimension of anxiety, when associated with a major
depressive episode, might modify patients’ memory perform-
ance profiles and result in not only a disruption of their explicit
but also of their implicit performances, especially when the
tasks involved are conceptual in nature. This consideration
could explain some of the results presented above. As far as we
know, only very few studies have addressed the role of clinical
elements such as affective blunting, psychomotor slowing or
anxiety on the memory performances of depressed patients.
However, it would appear that these dimensions have a harmful
effect on certain cognitive functions.
Current Research into the Evaluation
of Memory in Depression: Some
Methodological Propositions
In this section, we shall return to the various points set out
above that we consider to be relevant for a more thorough and
better examination of memory functions in depressed patients.
First of all, we should like to return to the distinction be-
tween perceptual and cognitive processes used in implicit and
explicit memory tasks. It appears that these different processes
are able to modify the performances of depressed patients in
implicit and explicit memory tasks. It would therefore seem to
be useful, following what has already been done among patients
with schizophrenia (Schwartz, Rosse, & Deutsch, 1993), to use
this dual dissociation in a group of depressed patients on the
basis of four memory tasks: word identification (data-driven
implicit memory test), cued recall (trigram completion: data-
driven explicit memory test), category production task (con-
ceptually-driven implicit memory test) and free recall (concep-
tually-driven implicit memory test). The hypothesis formulated
on the basis of the functional theories of memory supposes that
the conceptually-driven processes are impaired in depressed
patients whatever the mode used to investigate memory (im-
plicit or explicit). As we have seen earlier, the results that are
currently available for such patients do not all confirm this
assumption.
We saw above that the contamination of implicit memory
performances by explicit processes could, to some extent, ex-
plain the divergent results obtained by certain studies that have
revealed an impairment of implicit memory functioning in de-
pressed patients. In 1990, Bowers and Schacter used a ques-
tionnaire administered after a trigram completion task to show
that a certain number of their participants were fully aware of
the link between the encoding and the test phase. Mulligan
(2011), in a brief report, showed that conceptually-driven im-
plicit performance were lower in subclinical depressed indi-
viduals than controls only when participants were test-aware.
Another way to overcome this bias would be to use tech-
niques that attempt to reduce this awareness by employing,
among other things, appropriate instructions, specific encoding
and/or interfering tasks. To this end, Jacoby (1991) developed a
special procedure, the process dissociation procedure (PDP),
that permits improved control of the memory strategies used by
the participants. In one condition (inclusion), the use of the
PDP permits the automatic and controlled processes to work
together, whereas in another condition (exclusion) their respec-
tive actions can be contrasted. In this latter condition, partici-
pants are obliged to resort to controlled processes, thus ensuring
that the obtained effects are due only to the controlled processes.
The inclusion condition consists of an explicit memory test in
which the instructions require the participants to guess when
they are unable to remember. The exclusion condition consists
of a test in which the subjects are told not to name a previously
studied item as their response. This procedure has already been
used in the study of depression (Hertel & Milan, 1994;
McQueen et al., 2002). McQueen et al. (2002) showed disso-
ciation between automatic and controlled memory in depressed
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C. BESCHE-RICHARD
participants, with controlled processes altered. Moreover,
McQueen et al. (2002) showed that this deficit was more re-
lated to the number of past depressed episodes than to current
mood state.
The application of the PDP, as formulated by Jacoby, to
psychiatric patients, and in particular severely depressed pa-
tients, would seem to a problematic undertaking given that such
patients are known to tire very quickly. In effect, one of the
reasons for the difficulty of using the standard procedure lies in
the application of the experimental design during which the
inclusion and exclusion tests follow one another in a random
order during one and the same block of trials in the test phase.
This implies that the two instructions (inclusion and exclusion)
are maintained in memory since the subjects regularly have to
change from one instruction to the other. This, on its own,
represents a severe cognitive load for subjects whose informa-
tion processing is slowed and who exhibit memory difficulties.
Thus, in order to apply this method to depressed patients, we
suggest using a simplified procedure that has already been em-
ployed by Cermak, Verfaellie, Swenney, and Jacoby (1992)
among a population of amnesic patients and which makes use
of perceptual tasks that have been adapted for the conceptual
mode by Besche-Richard, Passerieux, Nicolas, Laurent, and
Hardy-Baylé (1999) for use in the study of schizophrenic dis-
orders. Furthermore, this simplified methodology makes it pos-
sible to evaluate conscious memory by testing the establish-
ment of a specific controlled mechanism, namely inhibition,
which a number of studies have found to be ineffective in de-
pressed patients (Benoit, Fortin, Lemelin, & Laplante, 1992;
Fossati, Ergis, & Allilaire, 2002).
The use of the paradigm developed by Tulving (1985) to take
account of two forms of recognition on the basis of introspec-
tive responses would make it possible to identify more clearly
the explicit processes that are impaired and gain a better under-
standing of these subjects’ recognition performances. When
participa nts use active memory re trieval mechanisms, th ey find
the information that is to be recovered and this memory inte-
grates the contextual elements that accompanied the encoding
of the information. In contrast, when recognition is based on a
feeling of familiarity, subjects know that they have already seen
the information but are unable to specify the associated contex-
tual elements. This opposition was operationalized for the first
time by Tulving (1985) in the R/K (Remember/Know) para-
digm and then subsequently taken up by Gardiner and Java
(1993). In this paradigm, participants taking part in a recogni-
tion task are asked to determine the nature of their psychologi-
cal experience associated with the recognition of each recog-
nized item. If the previously presented item is recognized very
clearly, then the participants have to give the response R to
indicate that they can clearly remember the circumstances un-
der which the item was studied, i.e. they are able to provide the
associated details. However, if the participants are sure of hav-
ing studied the target item but are unable to evoke a precise
memory in connection with it then they must respond K to in-
dicate simply that they have no doubts concerning the material
but cannot provide any details concerning the context associ-
ated with its presentation. In the model initially proposed by
Tulving, the R and K responses were associated with two dif-
ferent states of consciousness: R responses refer to autonoetic
consciousness while K responses are associated with noetic
consciousness. Within the framework of the “win-process”
theories presented above, the authors suggest that K responses
are based on perceptual processing or even on automatic infor-
mation processing mechanisms whereas the R responses would
tend to reflect explicit, conceptually-driven processes, or indeed
active, or even strategic, search processes based on the learning
context.
This paradigm seems to be of great interest for the investiga-
tion of memory impairments in depressed patients. This para-
digm has been used only in two studies (Ramponi et al., 2004;
Drakeford et al., 2010). Depressed patients displayed lower
levels of Remember for verbal and neutral facial stimuli con-
trary to Know judgments, and these memory performances
were related to the number of past depressive episodes. These
results support the hypothesis that memory deficits in depressed
patients are associated with a deficient recollection and a pre-
served familiarity processes (Drakeford et al., 2010). Ramponi
et al. (2004) have found a same set of results in a dysphoric
population.
Finally, we suggest that more attention should be paid to the
clinical factors that may influence the nature of the cognitive
performances observed in depressed patients. As far as the trait
vs. state character of the memory difficulties observed in de-
pressed patients are concerned, the studies conducted by Bazin
et al. (1994) & Bazin, Perruchet, and Féline (1996) are infor-
mative since they indicate that the impairments of explicit
memory can be attenuated by favorable clinical developments.
Furthermore, Channon et al. (1993) as well as Danion et al.
(1991) failed to reveal any differences in the memory function-
ing of patients who were or were not receiving psychotropic
treatment. It therefore appears that the administration of a bio-
chemical treatment is not responsible for the memory impair-
ments observed in depressed patients. This conclusion is sub-
stantiated by the results obtained by Bazin et al. (1994, 1996) in
which the improvement in the performances observed some
time after the acute episode related to patients who were still
receiving psychotropic treatment. It would appear that the re-
currence of major depressive episodes is associated with poor
recall performances unlike what has been observed in patients
suffering from their first depressive episode (Fossati, Coyette,
Ergis, & Allilaire, 2002; Fossati et al., 2004).
Above, we stressed the importance of the anxiety dimension
for memory performance. It seems to us that not enough atten-
tion has been paid to this dimension in studies of depressed
patients even though it is a clinical dimension that exists in a
high proportion of them. There is considerable overlap between
anxiety and depressive disorders, which is also expressed in a
certain degree of similarity in symptomatology, etiology, vul-
nerability factors (Drost et al., 2012). Similarly, factors such as
psychomotor slowing, affective blunting or the possible pres-
ence of psychotic symptoms might very well interfere with
implicit and/or explicit memory functioning. We know that
patients with psychotic symptoms present more severe illness,
were predictive of lack of remission (Buoli, Caldiroli, & Alta-
mura, 2013) and present more cognitive impairment than non-
psychotic major depressives for attention and executive func-
tioning (Schatzberg et al., 2000). It should be recalled that a
link between certain cognitive disorders observed in depressed
patients and various clinical dimensions has been established
(for example, executive deficits and psychotic symptoms, Fos-
sati, Ergis, & Alillaire, 2002; disappearance of the P3a compo-
nent [that indexes the automatic processing of information]
from the fronto-central sites in depressed patients who are char-
acterized by a high level of affective blunting and significant
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C. BESCHE-RICHARD
psychomotor slowing; in contrast, this P3a component is pre-
sent in depressed patients with a clinical description that is
characterized by a high level of anxiety and an impulsive di-
mension, Partiot, Pierson, Le Houezec, Dodin, Renault, & Jou-
vent, 1993; Partiot, Pierson, Renault, Widlöcher, & Jouvent,
1994; similar data has been obtained on the CNV [Contingent
negative variation] by Pierson et al., 1994). This data therefore
suggests that depression is not a homogeneous category either
at the cognitive or the clinical level. Depending on the domi-
nant clinical dimensions, it is likely that different cognitive
processes are impaired or preserved in depression. This general
observation undoubtedly also applies to mem ory performanc e s.
Conclusion
Memory disorders are an important component of the clinical
symptoms of depression. A specific neuropsychological evalua-
tion is an essential point in regard to the clinical profile (anx-
ious or psychotic symptoms associated) of depression and the
methodology of investigation of explicit and implicit memory.
In the future, in addition to the orientations mentioned above, it
is clear that the study of episodic memory in depression will be
linked to other cognitive functions such as self-identity (Sper-
durti et al., 2013), social cognition and metacognition (Rabin et
al., 2013). Finally, a better understanding of mnemonic function
in depressive illness will permit to develop specific methods of
cognitive remediation (Lee et al., 2013).
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