background Research on the composition and action of the genome ('genomics') can lead to new insights into aetiology, course and treatment of psychiatric disorders. Despite epidemiological evidence for involvement of genetic factors in psychiatric disorders so far no specific genes have been identified.
aim To give an overview of several methodological problems in genetic research today, leading to contradicting results, and possible ways to overcome them. This will be illustrated with research on the relation between polymorphisms in the serotonin transporter gene region (5-HTTLPR) and mood disorders.
method A limited search in literature was carried out using Medline (1966-May 2001), using as keywords '5-HTTLPR', 'polymorphism', 'mood disorder'.
results Positive as well as negative associations between a certain polymorphism (5-HTTLPR) and mood disorders were reported. In these studies several methodological problems could be pointed out .
conclusion To overcome the divers methodological problems, adjustments of psychiatric diagnostics are needed as well as new molecular biological tools. A more specific description of coresymptoms, clinical characteristics and so-called endophenotypes, can lead to the identification of more homogeneous subgroups of psychiatric disorders, which are more useful in genetic research. More genetic insight in aetiology of psychiatric disorders and functioning of psychotropics can lead to improved treatment strategies and prevention.