Berlin - Studies show that regularly smoking hashish or marijuana doubles the risk of developing schizophrenia, said Prof Peter Falkai of the Berlin-based German Society of Psychiatry, Psychotherapy and Neurology (DGPPN). Tetrahydrocannabinol (THC), the main psychoactive substance in hemp, is said to be responsible for the psychotic effect of cannabis.
Adolescents carry the greatest risk of lifelong mental illness. Cannabis consumption advances the onset of schizophrenia in people congenitally predisposed towards psychoses by about eight years - to the age of 17.7, on average.
"Many of those affected have trouble thinking clearly, hear voices talking about them or have delusions," explained Falkai, director of the Department of Psychiatry and Psychotherapy at Saarland University Hospital in Homburg.
"They then delude themselves into thinking they possess superhuman powers or are a religious or political personality," Falkai said.
Less conspicuous behavioural changes can also indicate schizophrenia. Many sufferers display social withdrawal or apathy.
