Do people with depressive symptoms learn fear less well?
Students with mild-to-higher depressive symptoms did not show a learned fear response in their skin conductance, even though they reported knowing which shape predicted a shock.
Source
Impairment in acquisition of conditioned fear in people with depressive symptoms
Study at a glance
- Design
- Human experiment — Within-subject differential Pavlovian fear conditioning (CS+ paired with shock on half its trials, CS- never) on day 1 and extinction 24 h later, comparing students split by Beck Depression Inventory score.
- N
- N=49 · 53 students enrolled; 4 excluded as skin-conductance non-responders, leaving 49 on day 1 and 44 on day 2. Group sizes after the BDI split are not stated directly.
- Population
- Healthy Chinese college students aged 18-30, split into those with (BDI > 4) and without (BDI <= 4) depressive symptoms
- Outcome
- Differential skin conductance response to CS+ vs CS- during acquisition and extinction; subjective US expectancy, nervousness and likeability ratings; fit of a hybrid associative-learning model
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What they did
College students first filled in questionnaires on depression, anxiety, childhood trauma, sleep and life events, and were split into groups with and without depressive symptoms using the Beck Depression Inventory. On day one they saw two shapes: one (CS+) was followed by a mild shock on half its presentations and the other (CS-) never was, while their skin conductance was recorded. The next day the shapes were shown without shocks to test fear recall and extinction, and a hybrid Rescorla-Wagner/Pearce-Hall learning model was fitted to each person's trial-by-trial responses.
What they found
Students without depressive symptoms showed larger skin conductance responses to the CS+ than the CS- by the end of conditioning, and this difference reappeared early on day two before fading with extinction. Students with depressive symptoms showed no CS+/CS- difference in either phase, suggesting they never acquired the conditioned fear physiologically. Both groups nonetheless rated the CS+ as more shock-predicting and more nerve-racking, with no group differences in these ratings, and the model's associability tracked skin conductance strongly in the non-depressed group (r about 0.69) but not at all in the depressed-symptom group.
The limits
What it doesn't show
The 'depressive symptoms' group was defined by a very low cut-off on a short self-report scale in healthy students, so the findings may not apply to clinical depression. Group conclusions rest on separate within-group t-tests rather than a direct test that the CS+/CS- difference was larger in one group than the other, and the group sizes are modest. The depressed-symptom group also had higher anxiety, trauma and poor-sleep scores; the authors argue these were in the normal range, but the design cannot rule them out, and a general blunting of skin conductance (rather than impaired learning) could produce the same pattern.
Key terms
- Differential fear conditioning
- A procedure where one cue (CS+) is paired with an aversive event and another (CS-) is not; learning is shown by a larger response to CS+ than CS-.
- Skin conductance response (SCR)
- A small change in the skin's electrical conductance caused by sweating, used as a physiological index of arousal and threat anticipation.
- Extinction
- The weakening of a conditioned response when the cue is repeatedly presented without the aversive outcome.
- Prediction error
- The difference between the outcome that happened and the outcome that was expected; in the Rescorla-Wagner model it drives learning.
- Associability
- In the Pearce-Hall model, how much attention and learning a cue receives, which rises when the cue has recently been followed by surprising outcomes.
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Quiz yourself
In this study, what served as the unconditioned stimulus (US)?
Common questions
If the depressed-symptom group rated the CS+ as more threatening, how can the authors say they did not learn?
Their verbal ratings showed they knew the rule, but their body's automatic arousal response did not distinguish the two shapes. The study separates conscious knowledge of the contingency from the physiological conditioned response, which often dissociate.
Why use partial reinforcement (shock on only half of CS+ trials)?
It slows acquisition and leaves unshocked CS+ trials whose skin conductance can be measured without the shock itself contaminating the response.
Does this mean depression protects against anxiety disorders?
No. The study suggests depressive symptoms and anxiety may relate differently to fear learning, but it only measured a lab task in students and did not study the development of any disorder.
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