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(12 versus 5.5 percent).
Other research shared by NIDA indicates
that about one in six (17 percent) of those who start using marijuana in adolescence become habitual users, and that 25 to 50 percent of daily users are addicted.16 Analysis of two waves of longitudinal data from approximately thirty to forty thousand individuals participating in the National Epidemiologic Survey on Alcohol and Related Conditions (NESARC) used a structured diagnostic interview to determine cannabis dependence in 25 percent of those who reported using cannabis on a weekly basis in the previous year.17 Again, men were more likely to be cannabis-dependent than women.
CANNABIS RISKS
Dopamine is a neuro-compound that signals
reward and enhances motivation. Much like other addictive drugs, the THC in marijuana increases the release of dopamine from the brain. Over time, this can lead to serious imbal- ances of this important neurotransmitter, with excessive cannabis intake adversely resulting in lower dopamine levels in the striatum part of the brain.18 (The striatum coordinates multiple aspects of cognition, including both motor and action planning, decision-making, motivation, reinforcement and reward perception.) For the cannabis-dependent person, dopamine deficits in the striatum result in cognitive impairment and memory and learning difficulties. De- creased striatal dopamine release also is predic- tive of subclinical psychopathology.18
Research indicates that cannabis use carries considerable risk of psychiatric illness and other serious outcomes. Summarizing ten years of epidemiologic, clinical and laboratory research, a 2009 report in The Lancet described a high probability of adverse effects from cannabis use, including “dependence syndrome, increased risk of motor vehicle crashes, impaired respi- ratory function, cardiovascular disease, and adverse effects...on adolescent psychosocial development and mental health.”19 Contrary to the notion that cannabis use exerts a calming ef- fect on all users, cannabis also can cause violent behavior20 and death (see sidebars).21 Perhaps even more troubling, one study found that can- nabinoids can introduce epigenetic changes that
SPRING 2019
can be passed on to future generations.22
Some people are aware that marijuana can cause paranoia during or after use, but many do not realize that the drug is associated with the onset of other disorders and symptoms such as anxiety, depression, social impairment, psycho- sis and schizophrenia,23,24 as well as lowering in- hibitions to experiment with other substances.25 The previously cited NESARC survey found that regular cannabis use “uniquely predicted the development of bipolar disorder, panic disorder with agoraphobia, and social phobia”
as well as overall declines in mental health.26 The Harvard Medical School’s Family Health Guide discusses two longitudinal studies that found a link between marijuana and depres- sion.27 First, a survey of sixteen hundred teenag- ers in Australia found that young women who had smoked marijuana weekly as teens were twice as likely as non-users to report depression when surveyed seven years later.28 The second study collected data from nearly two thousand young people in Baltimore in 1980 and followed up with the same respondents from 1994 to 1996.29 Young women who reported using mari- juana daily were five times more likely at follow- up to struggle with depression and anxiety. The study found that cannabis users who showed no signs of depression at the first encounter were four times more likely than initial non-users to
report depression fifteen years later.
Scientists know that the introduction of hallucinogenic substances to the brain and bloodstream carries a risk of psychosis—and the higher the level of use, the greater the hazard. Psychosis can entail hallucinations, hearing voices, seeing people who are not there and other breaks with reality, as well as agitation
and violent behavior toward oneself or others. Unfortunately, with the rise of ever more potent forms of cannabis, the risk of psychosis is increasing. A 2015 study in Lancet Psychiatry examined first-episode psychotic incidents in over four hundred adults age eighteen and older in south London and found that 24 percent of the cases were related to use of high-potency cannabis (with “high potency” defined as a THC content of around 25 percent).30 The authors also noted the ready availability of high-potency cannabis in the London area. Other United
Wise Traditions
With the rise of ever more potent forms of cannabis, the risk of psychosis is increasing.
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