MARIJUANA SCHIZOPHRENIA REPORT IS PURE BUNK

Will One Joint Really Make You Schizoid?

Maia Szalavitz, July 30, 2007

Just what did a new study on marijuana and schizophrenia actually say – and what did the media leave out?

Watching the media cover marijuana is fascinating, offering deep insight into conventional wisdom, bias and failure to properly place science in context. The coverage of a new study claiming that marijuana increases the risk of later psychotic illnesses like schizophrenia by 40% displays many of these flaws.
What are the key questions reporters writing about such a study needs to ask? First, can the research prove causality? Most of the reporting here, to its credit, establishes at some point that it cannot,though you have to read pretty far down in some of it to understand this.

Second – and this is where virtually all of the coverage falls flat –, if marijuana produces what seems like such a large jump in risk for schizophrenia, have schizophrenia rates increased in line with marijuana use rates? A quick search of Medline shows that this is not the case-- in fact, as I noted here earlier, some experts think they may actually have fallen. Around the world, roughly 1% of the population has schizophrenia (and another 2% or so have other psychotic disorders), and this proportion doesn’t seem to change much. It is not correlated with population use rates of marijuana.

MORE