Pubdate: Mon, 16 May 2016
Source: Vancouver Sun (CN BC)
Page: A9
Copyright: 2016 Postmedia Network Inc.
Author: Diane McIntosh
Note: Diane McIntosh is a clinical assistant professor in the 
department of psychiatry at the University of B.C.


The THC Potency Of Street Marijuana Has Increased, Writes Diane

In my psychiatric practice, I treat patients with psychotic illnesses
including schizophrenia. Most were born with a genetic vulnerability
to develop the disorder, but many share another important life
experience: they smoked pot from an early age.

Debate has raged across Canada about the impending
legalization/decriminalization of marijuana. Canadian physicians, in
their role as advocates for physical and mental health, have been
conspicuously absent from the debate. This troubling void in
leadership is apparent from the lack of informed discourse exhibited
across all forms of media. Our failure to educate Canadians regarding
the potential risks of street pot, particularly for a developing
brain, has important social, physical and psychological

Teens and their parents have been exposed to a steady stream of
pseudo-scientific nonsense about street pot: it's safer for kids than
alcohol, it improves driver safety, it cures cancer, it will usher in
world peace. Due to its accessibility and social acceptability, many
Canadians have come to believe pot is a benign herb. Teens are the
principal market for street pot, so there's a strong financial
incentive for pot-sellers to vehemently argue it's a safe, even
healthy, personal choice.

Tetrahydrocannabinol (THC) produces marijuana's "high," but it's not
your parent's pot anymore. Over the last several decades, street pot
has been selectively bred to increase THC potency from one to four per
cent to up to 40 per cent. The THC extract "shatter" (a.k.a. "the
heroin of marijuana") is a butane byproduct of cannabis yielding THC
levels up to 80 per cent. The heightened potency of THC in street pot
has been inversely mirrored by the reduction/elimination of
cannabidiol, the purported antipsychotic, anticonvulsant,
neuroprotective component of cannabis. Heightening THC potency and
eliminating cannabidiol has made street pot more impairing, more
addictive and more dangerous for a developing brain.

It is important to differentiate street pot from medicinal marijuana,
which has a balance of THC and cannabidiol. While there is
insufficient evidence for most physicians to feel comfortable
prescribing medicinal marijuana, there are situations where patients
have benefited from its use - for instance the treatment of
intractable childhood seizures, multiple sclerosis and severe and
treatment-resistant pain. I am concerned about the number of patients
that have become chronic pot smokers to get to sleep or to manage
anxiety without an adequate trial of treatments that have actual
evidence for their efficacy. Treatments with evidence are not limited
to medications, but include sleep hygiene and talk-therapy. The choice
to self-medicate with cannabis is a personal decision, but I think it
speaks to the appalling state of mental health services in Canada that
so many people feel they have no better options.

Schizophrenia is often a debilitating, chronic brain illness
associated with frightening psychotic symptoms, cognitive impairment
and declining functioning in all realms of life. Psychotic symptoms,
such as persecutory delusions and auditory hallucinations, usually
present during the teens or early 20s, but are often preceded by
prodromal, non-specific symptoms like depression, anxiety or social
withdrawal, sometimes years before psychotic symptoms are apparent.

Like all mental illnesses, the cause of schizophrenia is
multifactorial. Many have a genetic vulnerability to develop the
illness, but schizophrenia is believed to result from several "hits"
to a developing brain, from genetics to environmental exposures, like
infections and toxins, which may occur even before birth. Only a small
percentage of pot smokers develop schizophrenia, but there is an
abundance of high quality, well-replicated scientific evidence
regarding the association between THC and psychotic disorders.

Adolescence is a time of vital brain development, when brain cells
(neurons) are pruned and critical connections are made. Most mental
illnesses first present during the teen years. High THC levels, such
as those found in street pot, alter brain structure, size and
function, especially for frequent, heavy users. Neurons in brain areas
that are rich in cannabinoid receptors can be damaged or destroyed by

There is replicated clinical research demonstrating an earlier onset
of schizophrenia, by up to six years, in those who frequently use high
potency pot before age 15. Timing is critical because greater
emotional and social development before the onset of psychotic
symptoms is associated with less illness-related functional
impairment. If avoiding pot delays the onset of schizophrenia by
several years, this has a tremendous impact on educational attainment,
developing relationships, independence and engagement in treatment.

While no substance, including THC, is solely responsible for
schizophrenia, there are many large, long-term studies that lend
credence to the concern that THC is a trigger for psychosis in
vulnerable individuals. A 2014 study of more than 50,000 Swedish men
followed over 25 years concluded, "Schizophrenia patients with a
history of cannabis use had a significantly higher burden of lifetime
in-patient care than non-cannabis users. Not only does cannabis
increase the risk of schizophrenia, but also our findings indicate
that the course and prognosis of schizophrenia may be more severe than
schizophrenia cases in general."

Ongoing symptoms or repeated acute episodes of psychosis can worsen
the schizophrenia-related brain injury and functional decline. The use
of high-potency THC after diagnosis has been associated with a higher
relapse rate. Even if schizophrenia were inevitable, there is
compelling evidence for the benefits of remaining well for as long as
possible and avoiding pot after a diagnosis is established.

Some brains are more vulnerable than others and we have a limited
ability to estimate risk. Adults can make an informed decision about
whether to use pot. When guiding our children, however, we must
consider what they stand to lose. As a psychiatrist, the research
evidence is convincing, and so too is my clinical experience.

Avoiding pot during the teen years might reduce or even eliminate the
risk of psychosis.

As physicians, we need to step up and lead the scientific debate. I
support the legalization of marijuana. We need to tax it to help pay
for the physical and mental illnesses it causes and regulate its
availability. Most importantly, we need to educate Canadians about the
potential consequences of high potency pot on a developing brain. 
- ---
MAP posted-by: Jo-D