Genetics: The implications for forensic psychiatry

In 1953, Crick and Watson described the structure of DNA; the sequence of which holds the blueprint for all proteins involved in cellular structure and function, and which allows the transmission of genetic differences from one generation to the next. Understanding how genetic variation influences susceptibility to disease and individual differences in a variety of traits is now a major goal of genetics research. It is hoped that this will eventually lead to more effective ways to treat and prevent many of the major afflictions of mankind. In some disorders such as Cystic Fibrosis or Huntington's disease, the disease process can be attributed to a single gene mutation. However, most common disorders and traits are more complex and are likely to involve a number of genes, environmental factors and the interplay between them. Indeed this appears to be the case for many psychiatric disorders such as anxiety, alcoholism, substance misuse, schizophrenia, bipolar disorder, depression, and obsessive-compulsive disorder (Dinwiddle, 1994). In recent years many susceptibility loci or genes have been identified for a number of psychiatric disorders often failing to be replicated in subsequent studies. However emerging through the copious databases and publications, some susceptibility loci are showing some consistency in replication studies (Corsico and McGuffin, 2001; Owen, Williams and O'Donovan, 2004). Genes are also seemingly important in a number of behavioural traits including aspects of personality and cognitive abilities, which though not disorders themselves, may influence susceptibility to mental illness and maladaptive behaviours (Plomin, Price, Eley, Dale and Stevenson, 2002). However, yet again genes are only part of the story, and it is by understanding the interplay between genes and the environment that we are likely to discover the key processes involved.