Dr. Rasmussen Explains the Truth About Cannabis and Schizophrenia

I’m sure that many of you have already heard the mantra hailing past the naysayer’s camp of commercial medicine that cannabis smoking will increase your risk for psychosis. It’s a frightening argument which provides much needed ordinance for those “thought leaders” in medicine that are opposed to the use of cannabis for treating disease or the legalization of it.

In fact, it’s one of the main batteries used to discourage patients from trying cannabis for intractable seizure disorders-those who suffer from status epilepticus- which I have previously exposed. Fair enough contention. But is there any evidence, real evidence, that this is a tangible and significant risk?

I always find it amusing that certain highly educated, yet mulish, physicians will look for any reason to avoid recommending pot. Reaching for straws, with arms akimbo, if they can find a hypothetical motive to support their obstinance, they will run with it-even if the threat is insignificant for healthy patients.

For example, based on a handful of suggestive trials some physicians would see your child worsen from a rare seizure disorder rather than expose the child to a greater risk for developing schizophrenia (S) or cognitive impairment later in life should the patient start using marijuana.

Our protagonists will assure you that schizophrenics (I’ll use psychosis and schizophrenia interchangeably) only use cannabis to help reduce symptoms of their disease. That they smoke cannabis because it helps them to deal with their impairment in a much better way.

In this series we will uncover the truth by examining the most recent research on this controversial subject. Here we’ll discuss the risk for psychosis in young, chronic pot smokers. As you will see the peril is real but very limited to a small subset: those “at risk.”

Let’s start with a definition of schizophrenia the model psychosis.

From the illustrious Mayo Brothers Clinic:

Schizophrenia is a severe brain disorder in which people interpret reality abnormally. Schizophrenia may result in some combination of hallucinations, delusions, and extremely disordered thinking and behaviour.

Contrary to popular belief, schizophrenia isn’t a split personality or multiple personality. The word “schizophrenia” does mean “split mind,” but it refers to a disruption of the usual balance of emotions and thinking.

Schizophrenia is a chronic condition, requiring lifelong treatment.

The disorder generally manifests in late teens or early twenties, the “tweens.” There is a genetic component. Families with a schizophrenic parent have increased risk for children with this disease.


There is no known cure for schizophrenia. Patients are managed with powerful psychotropic medications, the classic and the atypical antipsychotics, for a lifetime. These medicines have proven to be a sword of Damocles for the unwashed masses given these drugs. The side effects are often at times so uncomfortable that some patients prefer suicide to a lifetime of being addled.

Moreover, these drugs promote heart disease and diabetes, stroke and heart attack. Class action suits have already been won. Therefore, in time, usually several decades, the patient often has a massive heart attack and often times it’s a “sudden death” event. I personally know of several people who have succumbed in this fashion. Then there are the devastating movement disorders that can occur with these drugs such as Parkinsonism and tardive dyskinesia. I bring this up because the sad state of psychiatry probably produces more illness than it helps.

You’ll hear both sides: that weed drives some users over the edge; or that pot acts as an antipsychotic. Referring to the latter, is there something in marijuana that helps schizophrenics deal with their disease? Perhaps with cannabis, traditional medications could be reduced or eliminated. Later on I’ll show you that indeed some cannabinoids may be the next “it girl” for treating schizophrenia.


A Times of London report stated that there are 210,000 people in the UK who suffer from schizophrenia, and a significant number of doctors feel that cannabis “caused” their condition.

Some of Britain’s most senior psychiatrists say the drug is now the “No 1 problem” facing mental health services. Psychiatrists in inner-city areas speak of cannabis being a factor in up to 80 per cent of schizophrenia cases, and mental health specialists are bracing themselves for an increase in the problem as reclassification is misinterpreted as an assurance that the drug is safe.[ref](http://www.schizophrenia.com/research/cannabis.htm) 07/06/2015[/ref]

Previously most authorities assured us that the use of cannabis among pre-psychotic patients with behavioral disorders was an attempt to self-medicate in the same fashion as one might use alcohol to help extinguish the anguish of psychosis.

In this segment we’ll uncover a disturbing, and often quoted, study which suggested that pot smoking caused a 300% increase in psychosis among that group. We’ll go over the significance of these findings and what they mean for the casual smoker of boutique buds and heady hashish.

Although most young people use cannabis without harm, a vulnerable minority experience harmful outcomes. A tenth of the cannabis users by age 15 in our sample developed schizophreniform disorder by age 26 compared with 3 per cent of the remaining cohort. Our findings suggest that cannabis use among psychologically vulnerable adolescents should be strongly discouraged by parents, teachers, and health practitioners. Policy makers and lawmakers should concentrate on delaying onset of cannabis use.I would say this is now the No 1 problem facing the mental health services in inner cities. In south London the incidence of psychosis has doubled since 1964.[ref]IBID[/ref]

From the above quote the term incidence means the number of new cases per a population, usually 100,000 people. There are at least 4 other studies that demonstrate the use of cannabis increases the risk for psychosis.


Now let me clarify something tucked inside the observations discussed in the above study. These are epidemiologic studies. They can only show an association not a causation for disease. Therefore, a casual glance shows a clear association with cannabis and mental illness. But can marijuana actually cause a user to become psychotic?

What seems to be occurring here is that kids with a predisposition toward mental illness, such as having a family member with schizophrenia, who smoke cannabis increase their chances for a psychotic break. Under these unusual circumstances marijuana behaves more like a trigger unmasking an already budding psychosis. For these “pre-psychotics” it’s not if but when they break so to speak. Cannabis seems to hasten the process.

That budding psychosis in the last study was called schizophreniform disease or “schizophrenia light.” But does marijuana actually cause this in patients not normally predisposed to the development of psychosis? In other words, can it make you psychotic even if you have no risk factors for it?

Not likely. Based on four large-scale, peer-reviewed studies previously conducted, scientists have concluded that there was a strong link between schizophrenia and cannabis consumption with a dark horse emerging from the scientific literature. From an LA Times article:

Data from four such studies suggest that cannabis use doubles the likelihood of developing a psychotic illness later in life.

But a few small studies have flipped the direction of causation, suggesting that a genetic predisposition to schizophrenia…is itself a risk factor for smoking pot. That might explain why pot use is perennially high (pardon the pun) among those diagnosed with schizophrenia.[ref](http://www.latimes.com/science/sciencenow/la-sci-sn-schizophrenia-marijuana-20140624-story.html) 07/06/2015[/ref]


A research team led by Robert Power, a psychiatry researcher at Kings College, published a most interesting study online in Molecular Psychiatry.

Their goal was to find important genetic links between schizophrenia and marijuana abuse.

We know that cannabis increases the risk of schizophrenia, lead author Robert Power, a psychiatry researcher at Kings College, said in a statement. Our study certainly does not rule this out, but it suggests that there is likely to be an association in the other direction as — that a predisposition to schizophrenia also increases your likelihood of cannabis use.[ref](http://www.schizophrenia.com/research/cannabis.htm) 07/06/2015[/ref]

LA Times author Geoffrey Mohan quips:

They analyzed the participants’ genome, looking for known variations that have been associated with schizophrenia. They found that those with the strongest genetic profile for schizophrenia risk also were more likely to use cannabis, and to use it in greater quantities. 

Madness, they suggest, may lead to reefer.

Did you catch that? A most fascinating conclusion: it suggests that cravings for cannabis and a marker for susceptibility to schizophrenia are located in the exact same region of your genome. I’m certain no one saw that coming. In other words those people most likely to develop schizophrenia are also genetically most likely to abuse marijuana.

A new study from the Harvard School of Medicine was published in Schizophrenia Research titled A controlled family study of cannabis users with and without psychosis.

So researchers from Harvard Medical School and the VA Boston Healthcare system got together to determine whether family risk for schizophrenia is a crucial factor underlying the association between the development of schizophrenia in teens who smoke marijuana.

The researchers recruited 282 subjects from the New York and Boston metropolitan areas who were divided into four groups: controls with no lifetime history of psychotic illness, cannabis, or any other drug use; controls with no lifetime history of psychotic illness, and a history of heavy cannabis use during adolescence, but no other drug use; patients with no lifetime history of cannabis use or any other drug and less than 10 years of being ill; patients with a history of heavy cannabis use and no other drug use during adolescence and prior to the onset of psychosis.[ref](http://psychcentral.com/news/2013/12/10/harvard-marijuana-doesnt-cause-schizophrenia/63148.html) 07/06/2015[/ref]

They concluded that:

The results of the current study suggest that having an increased familial…risk for schizophrenia may be the underlying basis for schizophrenia in cannabis users and not cannabis use by itself.[ref]Proal, Ashley C. et al. A controlled family study of cannabis users with and without psychosis. Schizophrenia Research , Volume 152 , Issue 1 , 283 – 288[/ref]

The above study also found a tendency for depression and bipolar disorder to be increased in cannabis users in both the patient and control samples. This finding implies that cannabis users are more prone to affective disorders than their non-using samples or vice versa.

However, only future research will be able to unravel this curious relationship.

Meanwhile, a group from the University of Manchester published their findings in 2014 which did not find marijuana aggravated or in any way influenced psychotic behavior. Like the above study, cannabis was associated more with depression/anxiety in the high-use group. I quote:

There was no evidence of a specific association between cannabis use and positive symptoms [voices], or negative symptoms [withdrawal], relapse or hospital admissions. However, a greater dose of cannabis was associated with subsequent higher depression and anxiety. Change in the amount of cannabis used was associated with statistically significant corresponding change in anxiety scores, but not depression. Additionally, reductions in cannabis exposure were related to improved patient functioning. Conclusions: Reducing cannabis may be directly associated with improvements in anxiety and functioning, but not other specific symptoms, [such as psychotic behavior].[ref]Schizophr Bull (2014) doi: 10.1093/schbul/sbu095 First published online: July 9, 2014[/ref]

Note the use of the word association in the above description. Once again even the “affective” disorders amongst marijuana users correlate well but we still cannot conclude that pot use causes these other problems any more than it causes schizophrenia.

To clarify the issues involved regarding psychosis and cannabis use we must make sure that the data does not lead us down the wrong path. To wit there are scores of damning epidemiologic studies showing how cannabis smokers have a greater chance of developing multiple drug addictions, cognitive impairment, cancer, psychosis, anxiety, depression, and of course let’s not forget bronchitis to name a few. Many of these findings are from epidemiologic studies.

Remember that none of these epidemiologic observations proves the point; these studies only show associations. To prove something we need double-blinded trials that control for all variables. Yet, unfortunately, for that to occur we need marijuana to be removed from its schedule one status so that human volunteers can receive pot legally for study. That’s one of the fixes we are currently in, and it’s the main reason why so much information within this field is confusing.

These studies are still significant and worthwhile but they must be interpreted in the proper context. No matter how impressive an association is within a population it remains to be seen if that association is actually a causation. From the CDCs website:

Epidemiology is the study of the distribution and determinants of health-related states or events in specified populations, and the application of this study to the control of health problems.


Epidemiology is a scientific discipline with sound methods of scientific inquiry at its foundation. Epidemiology is data-driven and relies on a systematic and unbiased approach to the collection, analysis, and interpretation of data. Basic epidemiologic methods tend to rely on careful observation and use of valid comparison groups to assess whether what was observed, such as the number of cases of disease in a particular area during a particular time period or the frequency of an exposure among persons with disease, differs from what might be expected. However, epidemiology also draws on methods from other scientific fields, including biostatistics and informatics, with biologic, economic, social, and behavioral sciences.

In fact, epidemiology is often described as the basic science of public health, and for good reason.

Epidemiology is also a statistician’s dream since the data can be manipulated to fit whatever theory one might be prejudiced with.

For example, let’s say an author of an observational study wants you to believe that TV causes heart disease. In his study he concluded that those who watch TV for more than four hours per day had a 50% increase in the risk for a heart attack.

OK fine, but other things to think about are the other slovenly habits these people have that may predispose them toward heart attacks. Perhaps TV watchers also eat junk food on a daily basis or maybe a greater percentage smoke cigarettes. Perhaps they don’t exercise. That’s why it’s important to understand that these epidemiologic studies in and of themselves say nothing that couldn’t be overturned with more rigorous trials.

However, it may turn out that cannabis does cause an increase in psychosis in those without a predisposition. It does not seem likely however based on what we know so far.

Let’s look at a different example: the proof that cigarette smoking caused lung cancer was initially discovered when epidemiologists noticed a much higher ASSOCIATION among tobacco users and lung cancer. The alarming number of cancers within all smoking populations were first noticed through epidemiologic investigations. That was followed with double-blinded studies to prove that is was an actual causation: that cigarettes caused lung cancer. That is now an accepted fact.

Same thing with the epidemiology of marijuana users and mental illness. We notice an increase in psychosis among users but the percentages are much smaller than the numbers of lung cancer patients seen in the above example, and the associations are much weaker.

For now all of the bad press with cannabis “causing” psychosis reflects simple epidemiological findings and nothing else.

Dr Deepak Cyril D’Souza sums it up:

It is likely that cannabis exposure is a “component cause” that interacts with other factors to “cause” schizophrenia or a psychotic disorder, but is neither necessary nor sufficient to do so alone.[ref]Eur Arch Psychiatry Clin Neurosci. 2009 Oct; 259(7): 413–431. Published online 2009 Jul 16.[/ref]

What are these other factors? What are the component parts?

For that, you guessed it, we need formal randomized, double blinded trials. Don’t hold your breath waiting as it may be years before the DEA grants easy access to cannabis for research. Based on what I have seen it takes about 6 years of red tape surfing before a research team gets their own legal marijuana for study.

That my good friends, is far too long.