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The Long-Term Consequences of Marijuana Use For The Brain

Study reveals how long-term marijuana use affects the brain’s structure and function.

Study reveals how long-term marijuana use affects the brain’s structure and function.

Regular marijuana users have increased connectivity in their brains, despite having some gray matter loss in areas related to addiction, a study finds.

The research, published in the Proceedings of the National Academy of Sciences, is the first to use multiple brain scanning techniques to examine both the structure and function of the brain.

Dr. Sina Aslan, one of the study’s authors, explained:

“What’s unique about this work is that it combines three different MRI techniques to evaluate different brain characteristics.
The results suggest increases in connectivity, both structural and functional that may be compensating for gray matter losses.
Eventually, however, the structural connectivity or ‘wiring’ of the brain starts degrading with prolonged marijuana use.”

The study involved 48 adult marijuana users who used the drug, on average, three times a day (Filbey et al., 2014).

They were compared to 62 matched non-users of marijuana.

The researchers found that the pattern of changes in both connectivity and structure of the brain depended on when and how often the drug was used.

Increases in connectivity were greatest when people began to use the drug and, the more they used it, the greater those increases.

Over time, though, an area of the brain called the orbitofrontal cortex is smaller in long-term marijuana users.

This area is crucial in how we make decisions and is central to how to brain processes rewards.

Taken together, this may explain why long-term marijuana users often seem to be doing reasonably well: structural losses in one area are being compensated for by connectivity gains.

It may also explain why the studies on marijuana’s effects on the brain have been so varied — some saying there is little damage, others more alarmist.

Dr. Francesca Filbey, who led the study, said:

“To date, existing studies on the long-term effects of marijuana on brain structures have been largely inconclusive due to limitations in methodologies.
While our study does not conclusively address whether any or all of the brain changes are a direct consequence of marijuana use, these effects do suggest that these changes are related to age of onset and duration of use.”

We still don’t know, though, the long-term effects of occasional marijuana use or whether the changes revert back to normal after drug-use is stopped.

Dr. Filbey concluded:

“We have seen a steady increase in the incidence of marijuana use since 2007.
However, research on its long-term effects remains scarce despite the changes in legislation surrounding marijuana and the continuing conversation surrounding this relevant public health topic.”

This study provides a fascinating insight into a controversial area.

Image credit: ashton

How Cannabis Causes Paranoia

Cannabis study provides insight into how to treat serious mental disorders.

Cannabis causes short-term paranoia and it’s not related to memory problems, a comprehensive new study has found.

The researchers discovered that after being given the main psychoactive ingredient in cannabis, THC (Δ9-tetrahydrocannabinol), participants became anxious, developed low self-esteem and experienced unsettling changes to their perceptions (Freeman et al., 2014).

The study’s lead author, Professor Daniel Freeman, said:

“The study very convincingly shows that cannabis can cause short-term paranoia in some people.
But more importantly it shines a light on the way our mind encourages paranoia.
Paranoia is likely to occur when we are worried, think negatively about ourselves, and experience unsettling changes in our perceptions.”

There were 121 people taking part in the study, none of whom were suffering from mental illness, but who had used cannabis before.

Two-thirds of them were injected with THC, while the remainder were injected with a placebo.

The amount was equivalent to a strong joint.

Half the people who were given the drug experienced paranoid thoughts, compared with 30% in the control group.

On top of this there were a variety of other psychological effects of the THC:

thoughts echoing,
altered perception of time,
anxiety,
various changes in perception such as sounds being louder than normal and colours brighter,
lowered mood,
negative thoughts about the self,
and poorer short-term memory.

When they looked at the results statistically, they were able to estimate what was causing the paranoia.

It turned out that it wasn’t a poorer memory:

“The increase in negative affect and in anomalous experiences fully accounted for the increase in paranoia.
Working memory changes did not lead to paranoia.
Making participants aware of the effects of THC had little impact.”

The scientists think the study of how cannabis causes paranoia will help the treatment of mental disorders which included delusional states, like schizophrenia:

“The clear clinical implication is that reducing negative emotion in patients with delusions, eg, by reducing the tendency to worry, testing out anxious fears, and increasing self-confidence, will lead to improvements in paranoia.
Also, the identification, normalization, and reduction of subtle anomalies of experience (eg, by reducing triggers and learning to tolerate the confusing sensory experiences) are clinically warranted.” (Freeman et al., 2014).

Fascinatingly, some people in the control group who were given a placebo also acted stoned, and it was difficult to tell the difference Freeman explained:

“…the placebo produced extraordinary effects in certain individuals.
They were convinced they were stoned, and acted accordingly.
Because at the time we didn’t know who had been given the drug, we assumed they were high too.”

Image credit: Alistair Holmes

Brain Changes Associated With Casual Marijuana Use

Brain region involved in reward, learning, pleasure and impulsivity may be affected by light marijuana use.

Young adults who smoked marijuana at least once a week showed changes in two brain regions associated with motivation and emotion, a new study finds.

The study, published in The Journal of Neuroscience, compared the density, size and shape of the amygdala and nucleus accumbens in 20 marijuana users with 20 non-users.

The 18-25-year old marijuana users smoked the drug at least once a week, but were not dependent on it.

The comparisons between the two groups showed that the nucleus accumbens — an area involved in reward processing — was larger and a different shape in marijuana users.

Dr Carl Lupica, who studies drug addiction, commented:

“This study suggests that even light to moderate recreational marijuana use can cause changes in brain anatomy.
These observations are particularly interesting because previous studies have focused primarily on the brains of heavy marijuana smokers, and have largely ignored the brains of casual users.”

This study builds on previous research on animals showing that even relatively low doses of tetrahydrocannabinol (THC) — marijuana’s main psychoactive component — can cause structural changes in the brain.

This study comes soon after research which reviewed 120 studies on the effect of marijuana use on the teenage brain.

The conclusions of that report were that for those with particular vulnerabilities, like neuroticism and anxiety, marijuana is not as harmless as many assume.

Findings about the connection between marijuana use and very serious mental illnesses, like schizophrenia, have been unclear, with some saying it can be a causative factor in those who are vulnerable while others find little or no evidence.

Unfortunately, what we currently know about the effects of marijuana on the brain is mostly from heavy users of the drug.

This study hints, however, that even relatively causal use of marijuana may cause changes in the brain.

We don’t yet know what the implications of these changes are, but they certainly warrant further investigation.

→ The effects of regular cannabis use on creativity.

Image credit: Peter Briones

Marijuana Does Not Cause Schizophrenia

New study on marijuana use finds little evidence that the drug causes schizophrenia.

The study, published in Schizophrenia Research, and carried out at Harvard Medical School, compared families with and without a history of schizophrenia (Proal et al., 2013).

It comes in response to much research which has linked marijuana use with schizophrenia (e.g. Moore et al., 2007).

These previous studies, however, could not rule out the possibility that people who are prone to developing schizophrenia are also more likely to use marijuana.

In other words: marijuana may not cause schizophrenia, but it might be that people who are prone to developing schizophrenia are more likely to use marijuana. This would explain the link that’s been found in the studies.

In the new study, by comparing families with and without a history of marijuana use, the Harvard researchers were able to address this question.

They recruited four groups:

87 non-psychotic people who had used no drugs.
84 non-psychotic people who had used marijuana.
32 patients who had schizophrenia but hadn’t used drugs.
76 patients with schizophrenia who had used marijuana.

They then looked at the relatives of those with schizophrenia in comparison to the relatives of those in the control groups.

The results showed an increased risk of developing schizophrenia in the relatives of patients who already had schizophrenia, whether or not those patients used marijuana.

This study, then, finds no evidence that marijuana is associated with developing schizophrenia. The authors conclude that:

“…cannabis does not cause psychosis by itself. In genetically vulnerable individuals, while cannabis may modify the illness onset, severity and outcome, there is no evidence from this study that it can cause the psychosis.” (Proal et al., 2013).

Is it safe?

One study, of course, is not the end of this debate.

For one thing this study can’t tell us anything about the interaction between the genetic predisposition to develop schizophrenia and marijuana use.

Many researchers still believe that marijuana use may be a factor in the onset of schizophrenia in those who are at risk.

Certainly, there is plenty of other evidence out there that marijuana is not the totally safe drug that many teenagers perceive it to be.

→ Read on: Teen Myth: Marijuana is a ‘Safe Drug’.

Image credit: Eugenia Lyakhova

Teen Myth: Marijuana is a ‘Safe Drug’

New research challenges the common teenage view that marijuana is a ‘safe drug’ in comparison to alcohol and tobacco.

Especially among teens, there is perception that, in comparison to ‘dangerous’ legal drugs like alcohol and tobacco, marijuana is relatively safe.

Surveys suggest that one-third of high school seniors have tried pot in the last year and less than half of 17-year-olds believe the drug is harmful.

A new review of the evidence, however, to be published in Neuropharmacology, suggests the drug may have harmful consequences for the growing adolescent brain.

Hurd et al. (2013) reviewed data from more than 120 studies to examine the relationship between marijuana use and the teenage brain.

They find that marijuana may be harmful for a particular type of vulnerable adolescent, possibly leading to behavioural problems and addiction.

One of the study’s authors, Didier Jutras-Aswad explained:

“It is now clear from the scientific data that cannabis is not harmless to the adolescent brain, specifically those who are most vulnerable from a genetic or psychological standpoint. Identifying these vulnerable adolescents, including through genetic or psychological screening, may be critical for prevention and early intervention of addiction and psychiatric disorders related to cannabis use.”

While the research on the long-term effects of marijuana use, especially in vulnerable populations, is still relatively young, the warning signs are mounting:

A study of 1,037 individuals followed from birth found that persistent cannabis use was associated with cognitive decline over the years. More worryingly these problems continued even after drug use ceased (Meier et al., 2012).
A review of many studies on marijuana use has found that it can damage the encoding, storage, manipulation and retrieval mechanisms of memory (Solowij & Battisti, 2008).

Teenagers should be aware that, for those with particular vulnerabilities, like neuroticism and anxiety, marijuana is not as harmless as many assume.

Image credit: miggslives

Does Cannabis Cause Psychosis?

An excellent balanced report in The Independent:

“First, there has been no increase in schizophrenia in this country despite a massive increase in cannabis smoking. Second, there is no evidence that cannabis-growing populations such as Jamaica have a higher incidence of psychosis. Third, you can show an association [between the drug and the illness] but you can’t show a cause.”

The Independent