Illegal Drugs

HC Deb 11 March 2004 vol 418 cc1692-3W

Mrs. Iris Robinson

To ask the Secretary of State for Health what assessment he has made of the possible link between illegal drug use and the development of psychosis later in life; and if he will make a statement. [152364]

Miss Melanie Johnson

Recent research of note in this area has explored whether there is any causative link between early cannabis use and later development of psychosis, but such a link has not been conclusively proven. However, the recent epidemiological research on the issue of earlier use of cannabis and risk of later development of schizophrenia, 'schizophrenic symptoms' and 'schizophreniform disorder' has shown a stronger association than was previously evident from published studies. The British Medical Journal editorial accompanying the publication of key research papers in November 2002 concluded that: whether the use of cannabis triggers the onset of schizophrenia or depression in otherwise vulnerable people or whether it actually causes these conditions in non-predisposed people is not yet resolved.

While a number of illegal drugs, particularly amphetamines and cocaine (and to a lesser degree cannabis), are well-recognised in causing short-lived psychotic symptoms and signs there is no conclusive proof of causation of psychosis in later life. It is difficult to exclude confounding factors in carrying out such long-term research on, where such drug use would also be only one of a number of risk factors. It is also difficult to differentiate the role of such drugs in possibly precipitating psychosis in a pre-disposed individual from causation in someone not otherwise pre-disposed.

The Department has commissioned the National Addiction Centre to review the evidence regarding the harmful effects of drugs of abuse and this is published as a Department of Health document, Dangerousness of drugs (2003). This describes a wide range harmful effects of illegal drugs. A copy is available in the Library.

It is widely recommended by clinicians that anyone at risk of psychosis should avoid any drugs that can cause acute psychotic symptoms.

The Department continues to monitor research in this area and has a range of expert advisors to continue to inform policy.