This leads to poorer brain performance. The finding, which must still be confirmed, emerged from a study involving memory tests of people with schizophrenia and their well siblings. Symptoms include hallucinations, delusions, social withdrawal and loss of social skills. Its cause is a mystery, but some evidence suggests that it is chiefly heritable, though with strong environmental factors. Several chromosomal regions have been implicated with the disorder, but no genes have yet been definitely linked to it.
Some scientists suspect that the chemical messenger dopamine is in some way responsible.
Dopamine plays a crucial role in the brain's activity. It comes in one of two forms. The most common variant, 'val', reduces dopamine activity in the prefrontal cortex, while the somewhat less common form, 'met', increases it. To investigate the relationship between these gene variants, brain activity and schizophrenia, Daniel Weinberger and colleagues from the National Institutes for Mental Health, US, conducted brain imaging studies on sufferers and their relatives. They found that their COMT genes influenced the brain's efficiency in the prefrontal cortex region, the area of the brain that plays an important role in memory.