Explanations of depression

Biological approach assumes depression (like all dysfunctional behaviour) is caused and can be explained by biological functions.

Depression can be due to:

• Low levels of serotonin and high levels of cortisol (neurotransmitter imbalance).
• Genes - may create a predisposition to depression.

Wender et al:

• Investigate contribution of genetic + environment factors in aetiology of mood disorder.
• Psychiatric evaluations of adoptive and biological relatives of 71 adult adoptees w/ depression.
• W/ a control group that were psych normal.
• Eight fold increase in unipolar depression among biological relatives of depressed adults and 15 fold increase in suicide.

Diathesis-stress model:  there is an existing predisposition to depression and the expression of the gene is triggered by a life event.

Behaviourists believe that all behaviour is learnt and therefore depression is learnt. This can be through:

• Imitation of a depressed parent.
• Associating depression with certain life events or situations (classical conditioning).
• Positive reinforcement for depressive behaviour (operant conditioning).

Lewinsohn - depression caused by a reduction in positive reinforcement:

• Comparing the amount of +ve reinforcement experienced by depressed and non-depressed patient.
• Over 30 days where p's completed a pleasent activities scale - rating twice, one for pleasentness and one for frequency 1-3. Also rated depression using depression adjectives checklist.
• More sig. +ve correlations between mood ratings and pleasent activites. However, individual differences vary.
• Appears to be a link between reinforcement from +ve activites and mood but further research needed. 

Cognitive approach assumes that depression is caused by faulty and illogical thinking - negative thinking. (E.g. Beck's cognitive triad - negative thoughts about onself, the world and the future.)

Beck et al:

• Understanding cognitive distortions in patients with depression.
• Face-to-face interviews with retrospective reports of patients' thoughts before the session as well as spontaneous thoughts during the session. Some patients kept diaries of their thoughts and brought that to the session. Records were compared with verbalisations of non-depressed patients.
• Key themes appeared in depressed patients: low self-esteem, self-blame, paranoia, overwhelming responsibilities.
• They had stereotypical responses to situations and felt less attractive and intelligent.
• They felt unlovable and alone.
• These distortions tended to be automatic, plausible, involuntary and persistant.

Thus patients have cognitive distortions that deviate from logical thinking even in mild depression.