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01-09-2011 | Mental health | Article

Excessive cannabis use linked to earlier age at BD onset


Free abstract

MedWire News: Excessive use of cannabis is associated with an earlier age at disease onset in patients with bipolar disorder (BD), research shows.

"The age at onset (AAO) of BD varies from adolescence to mid-adulthood, but the reasons for the variation are not fully known," write Trine Lagerberg (Oslo University Hospital, Norway) and team in the European Archives of Psychiatry and Clinical Neuroscience.

They add that a number of factors, such as a family history of affective disorder, have been associated with an early AAO in BD patients, but it is not known whether substance use is associated with AAO in such patients.

To investigate, the team studied 151 patients, aged 18-65 years, with bipolar I or II disorder who were receiving psychiatric treatment and participated in the Thematically Organized Psychosis study.

All of the participants completed questionnaires on lifetime substance use, with a particular focus on alcohol and cannabis use. Patients who met criteria for a Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition (DSM-IV) substance use disorder, or who had used substances on a predominantly daily basis for a minimum of 4 years during any period of their lives were considered excessive substance users.

In total, 28 patients reported excessive alcohol use, 35 reported excessive cannabis use, and 85 reported no excessive use of substances during their lives.

The mean AAO of BD in these groups was 27.0, 19.5, and 22.5 years, respectively.

After accounting for factors such as gender, type of BD, a family history of affective/psychotic disorders, and excessive use of substances other than alcohol or cannabis, the team found that excessive use of cannabis, whether it occurred before or after the onset of BD, was significantly associated with an earlier AAO compared with no excessive use of substances.

Excessive use of alcohol or other substances were not significantly associated with AAO in multivariate analyses, although excessive alcohol use was significantly associated with a later AAO compared with excessive cannabis use.

Lagerberg and team conclude: "Lifetime use of cannabis predicted an earlier onset, independent of the sequence of onsets.

"This indicates that an early onset may increase the risk of cannabis use and that cannabis use may trigger bipolar disorder in vulnerable individuals."

By Mark Cowen

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