The missing grey cells that turn people into obsessives

Scientists in the UK have discovered new evidence as to why obsessive compulsive disorder (OCD) runs in families.

The Cambridge University researchers have found changes in the brain that are linked to obsessive compulsive disorder and say people with OCD and their close family members share distinctive patterns in their brain structure.

OCD is a relatively common condition which affects 2 to 3 per cent of the population.

OCD is characterised by obsessions and constantly repetitive actions and people with the disorder can suffer great distress and anxiety.

Sufferers experience recurrent thoughts about subjects such as contamination and germs and often take part in rituals, such as repeated hand-washing, checking windows are locked or lining items up in a specific order.

They may also suffer recurrent, unwanted thoughts.

Although OCD is suspected to run in families, the gene responsible has yet to be found.

A Cambridge team from the Brain Mapping Unit at the university decided to examine whether the effects of the gene might be detectable in the brain structure of patients and their unaffected relations.

The team led by Ed Bullmore used magnetic resonance scanning of the brains of 31 OCD patients to measure their ability to perform simple tasks involving brain and hand.

This involved a computerised test which meant pressing a left or right button as quickly as possible when arrows appeared; when a signal noise sounded, they had to try and stop their responses, with the aim of measuring their ability to halt repetitive behaviours.

They compared the 31 scans with those taken of 31 first-degree relations who were unaffected by OCD - sisters, brothers, parents, and children and 31 unrelated healthy people.

The research team found that both the OCD patients and their close relations did worse on the computer task than the control group.

Earlier research has shown similar results, suggesting that when a pattern of actions is established, people with OCD find it hard to stop them.

When the performance on this test was compared with MRI scans, it was found that performing poorly was associated with decreases of grey matter in brain regions important in suppressing responses and habits and this appeared to be the case in actual OCD cases, and in close relations who did not suffer the disease.

The researchers say this suggests that there may be additional factors that trigger the condition in susceptible people.

According to Lara Menzies, the lead author of the paper, impaired brain function in the areas of the brain associated with stopping motor responses may contribute to the compulsive and repetitive behaviours that are characteristic of OCD.

Menzies says these brain changes appear to run in families and may represent a genetic risk factor for developing the condition.

The researchers say as the current diagnosis of OCD is subjective, knowledge of the underlying causes may lead to better diagnosis and ultimately improved treatments.

The findings are published in the journal Brain.