1. Mood Disorders Biological explanations Genetics
Neurochemical abnormalities

2. 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

3. 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

4. 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

5. Mood Disorders - Neurochemical

6. 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)

7. 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

8. 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?