© Banff and Buchan College 2004 Depression – Biological Factors

Mood Disorders Biological explanations –Genetics –Neurochemical abnormalities

Mood Disorders – Genetic Zubenko et al (2001) –Family history – 50% of FD relatives, 25% of SD relatives also had mood disorder –Relatives had increased risk of suicide & liver disease McGuffin et al (1996) –MZ 46%, DZ 20% –MZ concordances substantially inflated in more serious cases

Mood Disorders – Genetic Depression tends to run in families The closer the relationship with a sufferer, the more likely a person will have a mood disorder Genetic evidence is strongest for most severe forms of the disorder Concordance rates also indicate a substantial environmental contribution

Mood Disorders - Neurochemical Abnormality in neurochemicals Too much or too little of some chemicals e.g. serotonin affects the functioning of the brain – this might have an effect on emotion regulation

Mood Disorders - Neurochemical

Noradrenanaline (NA) –Too little leads to depression, too much to mania (catecholamine hypothesis) Serotonin (5-HT) –Regulates NA activity, so too little allows abnormal fluctuations in NA (permissive amine hypothesis) Dopamine (DA) –Involved in reinforcement, so too little results in anhedonia (dopamine hypothesis)

Mood Disorders - Neurochemical Some evidence (but not all) suggests that mood disorder patients have abnormal levels of NA & 5-HT –Might be sensitivity to neurotransmitters that matters, not raw levels in brain –Interactions between neurotransmitters are poorly understood – likely to be complex –Problems with direction of causality

Mood Disorders - Neurochemical Drugs that alter brain levels of NA & 5-HT are effective in treating depression in about 60% of cases –So what about the non-responsive patients? –Relapse when drugs are discontinued? –Treatment-aetiology fallacy?

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