A number of studies have shown that antipsychotic drugs can lead some people to develop obsessive-compulsive symptoms. There is known to be a genetic link to obsessive-compulsive disorder (OCD) and genetic factors are also thought to be involved in the way different people react to antipsychotic drugs. Substances called glutamates (which occur naturally in the body) are thought to play a part in the development of OCD and a gene called SLC1A1 is thought to play a part in how the brain deals with them. A team of researchers from South Korea compared 40 people taking antipsychotics who had developed OCD with 54 people who had taken the drugs but not developed it. They found that the group who had developed OCD were more likely to have variations in the SLC1A1 gene.
Kwon, Jun Soo ... [et al] - Association of the glutamate transporter gene SLC1A1 with atypical antipsychotics-induced obsessive-compulsive symptoms Archives of General Psychiatry November 2009, 66(11), 1233-1241