Pubdate: Wed, 21 Aug 2013
Source: Manawatu Standard (New Zealand)
Copyright: 2013 Manawatu Evening Standard
Contact:  http://www.stuff.co.nz/manawatu-standard/
Details: http://www.mapinc.org/media/1057
Authors: Amir Englund and Robin MacGregor Murray
Page: 12

THE PSYCHOLOGICAL CONSEQUENCES OF PUFFING ON POT

Researchers are getting a better understanding of the effects of
cannabis use on mental health, but the definitive answer remains hazy,
write Robin MacGregor Murray and Amir Englund.

Is cannabis harmful to mental health? That question has provoked much
debate over the years, often generating more heat than light. The
bottom line is this: Within the scientific community, there is a
general consensus that most people who use cannabis will not develop
significant mental health problems. Certain individuals, however, are
more susceptible to the negative effects of its use.

It was long thought that cannabis was a relatively harmless drug and
that concerns about its use were overstated. Some psychiatrists had
reported that excessive use could lead to a psychotic state, including
hallucinations, delusions and thought disturbance.

But the first significant indication of a link between cannabis use
and psychotic illness came only in 1987, from a large Swedish study
that followed more than 50,000 subjects over 15 years. Reported
cannabis use at the study's start increased the likelihood of being
diagnosed with schizophrenia in the next 15 years. The greater the
use, the higher the likelihood of being diagnosed.

Curiously, this finding did not spur much interest and no similar
studies were reported until 2002. Since then, however, many studies
have explored the association between cannabis use and psychotic illness.

In 2007, a compilation of the best studies concluded that frequent (
daily) cannabis use doubles the risk of a psychotic outcome. Since the
lifetime prevalence of a psychotic illness is roughly 1 per cent of
the population, daily cannabis use would increase this to 2 per cent.

Of course, the existence of a positive correlation between cannabis
use and psychosis, does not allow us to draw a direct causal link
between the two. Psychosis could cause cannabis use, rather than vice
versa, or an unknown mediating factor could cause both cannabis use
and psychosis.

Other factors already complicate the relationship. For example, the
age at which cannabis use begins appears to be an important factor.
People who started using cannabis before the age of 16 have a higher
risk of psychosis compared to those who start after 18. This is in
line with biological evidence suggesting that the maturing brain is
more susceptible to the negative impact of cannabis.

Moreover, different strains of cannabis pose more or less risk for
psychosis. A comparison of the two most common types of cannabis in
the United Kingdom, hash and sinsemilla (" skunk"), found that using
skunk implied a significant greater risk of psychosis, while hash did
not.

The explanation for this difference lies in the composition of the two
main components of cannabis, delta- 9- tetrahydrocannabinol ( THC) and
cannabidiol ( CBD). Skunk in the UK has high levels of THC, while
being virtually devoid of CBD; hash, on the other hand, has roughly
equal quantities of the two components.

Some studies have explored the role of cannabis use in disorders, such
as depression and anxiety. While little sign of a link has been found,
there is better evidence for the addictive potential of cannabis.

It is generally accepted that frequent and prolonged cannabis use
impairs cognitive functioning, but that these effects are reversible
following abstinence of three to 12 months. However, a recent study
that followed people from birth to age 38 found that those who started
using cannabis early, every day and for several years had a permanent
eight-point drop in IQ scores. ( The study has not yet been
replicated.)

A final, and often-overlooked, source of harm to mental health
associated with cannabis is the legal fallout of being caught with
it.

So, does cannabis use harm mental health? Yes and no. Much depends on
how old you are when you start, your genes, and how much, how often,
and what kind you use  and, of course, on whether you get caught.

Project Syndicate
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MAP posted-by: Matt