This article in today's Independent (based on recent articles in Nature) claims that schizophrenia and manic depression have a common genetic basis. This discovery is, they claim, "at odds with the orthodoxy in psychiatry stating that the two conditions are clinically distinct". It will not, however, come as a surprise to many people who have experience of working with mental health problems, students on my mental health module. Enlightened practitioners have come to realize that such terms do not necessarily have any direct link to dictinct pathologies and are in fact just ways of categorizing groups of symptoms. Some patients are given more than one diagnostic category at different times and this can be very confusing for them. It is much safer to say that someone who has symptoms such as delusions or hallucinations is suffering from a psychosis. The article also points to the involvement of areas of the genome associated with the immune system and this would help to explain the variations in succeptibility associated with the time of year someone is born. Links have also been found with genes involved in growth of nerve cells and production of neurotransmitters.
The work is based on analysis of gerntic material from 15,000 pateints and 50,000 'healthy' subjects.
The study points to a common vulnerability to the two conditions but does not explain why people develop one condition or the other. It also supports the stress vulnerability model as inheritance is only claimed to account for 80% of the risk.