Smoking marijuana affects your ability to work

Cannabis: Risks of Non-Medical Use

Cannabis is the most widely used illicit drug in the world. In Germany, it is used annually by around 4.5% of all adults. Intensive cannabis use is associated with health risks.

Depending on age, dose, frequency, form of application, situation and individual disposition of a person, different acute consequential damages can occur through cannabis use. These include panic attacks, psychotic symptoms, impaired alertness, lack of concentration, impaired motor coordination and nausea.

A combination of motivational support, cognitive behavioral therapy and contingency management are currently the most effective treatment approaches for cannabis addiction.

Cannabis is the most commonly consumed illicit drug around the world; in Germany, about 4.5% of all adults use it each year. Intense cannabis use is associated with health risks.

Various medical conditions can arise acutely after cannabis use, depending on the user’s age, dose, frequency, mode and situation of use, and individual disposition; These include panic attacks, psychotic symptoms, deficient attention, impaired concentration, motor incoordination, and nausea.

At present, the most effective way to treat cannabis dependence involves a combination of motivational encouragement, cognitive behavioral therapy, and contingency management.

Cannabis was recently legalized for recreational use in some US states. At the same time, scientific knowledge of the therapeutic potential of cannabis-containing drugs is improving. Against this background, it is to be expected that patients will want to be informed more often by their doctors and other professional groups in the health system about the health risks and medical benefits of cannabis.

Cannabis is the most widely used illicit substance in the world. The United Nations estimates that between 125 and 227 million people worldwide use cannabis. According to the latest national epidemiological addiction survey, 4.5% of German adults used cannabis in the last year. Use is particularly common among 18 to 20 year-olds (12-month prevalence: 16.2%). An estimated 1% of the EU population (twelve million) use cannabis on a daily basis. Overall, around 9% of all people who have ever tried cannabis develop addiction. This rate is 17% if cannabis use begins in adolescence and 25 to 50% if cannabinoids are used daily.

Cannabis is mostly consumed as “marijuana” (dried flowers and leaves) or “hashish” (delta-9-tetrahydrocannabinol [THC] -containing resin of the inflorescences). THC-containing oil is less frequently ingested in food. According to police reports, cannabis plants are increasingly being grown in their own country and are being imported less often.

The content of THC, the main psychotropic substance in cannabis, has increased significantly over the past decade. Another active ingredient, cannabidiol (CBD), is no longer present in many breeds. This is attributed, among other things, anxiolytic, antipsychotic, anti-inflammatory, antiemetic and neuroprotective effects, which can possibly offset the aversive effects of THC. The consumption of cannabis products with a high THC and at the same time low CBD content is ascribed to undesirable effects in people with a corresponding predisposition. The total number of addiction treatments for cannabis use is increasing in Europe and the United States.

Cannabinoid interference

When smoking cannabis, the THC enters the bloodstream through the lungs. It penetrates the internal organs and the brain within minutes. There the THC unfolds its effect mainly via the cannabinoid receptors CB1. These are most commonly located in cerebral regions associated with body movement, learning, memory, and the reward system. Smoking herbal cannabis can lead to acute intoxication. The effect depends on the composition of the preparation, the dose, the frequency, the form of application, the situation as well as the individual disposition and consumption experience of a person. The symptoms recede after the pharmacological effects have subsided. Cannabis can be detected in the urine via the metabolite THC-COOH for two to six weeks after stopping consumption.

A meta-analysis reported slight negative effects on learning and memory in non-abstinent, habitual users. These effects were still detectable after at least 24 hours of abstinence. Attention and reaction speed were not affected. A more recent meta-analysis also provides evidence of mild, global cognitive impairments in acute cannabis use. Compared to abstainers, non-abstinent cannabis users had slight limitations in the following areas:

abstract thinking or the ability to perform executive functions




psychomotor functions.

These differences were no longer detectable after at least one month of abstinence. The effects may be reversible in adults. Other studies show that cognitive impairments can still be present even after four weeks of abstinence, especially if the consumption of cannabis in adolescence begins early. Persistent slight to moderate deficits were found in the following areas:

psychomotor speed



Planning ability.

Between 50 and 90% of all cannabis addicts have a life history diagnosis of another mental disorder or a health disorder caused by alcohol and other substance use. Some studies suggest a positive relationship between cannabis use and bipolar disorder or between increased manic symptoms and cannabis use. The study situation in depression is less clear.

Early, regular, long-term and high-dose consumption of cannabinoids, in combination with other stressors such as experiences of violence and abuse in childhood or psychoses in the family of origin, has been associated with an increased risk of psychotic disorders. With a certain genetic pattern, cannabinoids and stress, as shown in animal experiments, can promote the development of psychosis.

Various studies have shown a connection between early, regular cannabis use and continued use of other illegal drugs or alcohol. However, there is no empirical evidence that cannabis acts as an access substance for the use of other substances (“gateway hypothesis”).

Many of those affected may use cannabis to relieve unwanted mental or physical symptoms. This has been reported for patients with post-traumatic stress disorder or chronic pain. Cannabis is also increasingly smoked by people with schizophrenic psychoses, possibly due to the antipsychotic effects of cannabidiol, and increases the risk of more and longer paranoid syndromes and symptoms of intoxication in 40% of users.

Further research is needed to clarify the causality of the links between cannabis use patterns and adverse sequelae. Confounding variables in particular should be better controlled in future studies.


Cannabis use is the leading cause in Europe that patients first started drug treatment for the use of illegal substances. The number of first treatments rose from 45,000 to 61,000 between 2006 and 2011 and stabilized at 59,000 in 2012.

In Germany, cannabis-related disorders are mostly treated on an outpatient basis, for example in addiction counseling centers, addiction clinics or specialized practices. Even the uncomplicated withdrawal usually takes place on an outpatient basis.

Qualified inpatient treatment is indicated for:

complicated course of intoxication

severe withdrawal syndrome and / or severe secondary disorders

high risk of relapse

comorbid mental disorders.

The therapy consists of acute and post-acute treatment. In acute therapy (duration: two to four weeks; for adolescents four to twelve weeks), physical detoxification, diagnostics, treatment of withdrawal symptoms as well as clarification and, if necessary, treatment of comorbid disorders can take place. In addition to intensive supportive discussions and daily structuring with, if necessary, psychopharmacological support, the patient is motivated to take up abstinence-stabilizing therapy if the willingness to treat is still lacking in the case of impaired psychosocial functional level (i.e. difficulties in organizing everyday life and structuring the day).

More complicated courses of intoxication can be characterized by panic attacks, psychotic or delirious symptoms. In these cases, discussions with the patient and, if necessary, a time-limited administration of antipsychotics (preferably atypicals) and / or sedatives are helpful.

The rehabilitative post-acute treatment (duration: three to nine months) serves to ensure abstinence, relapse prevention, psychological, social and professional stabilization and the treatment of comorbidities. For young people, educational support, reintegration into school and clarification of the family and housing situation are also relevant.

A meta-analysis and several systematic reviews of randomized controlled studies show that short interventions (six to twelve sessions) with combinations of motivational support, cognitive-behavioral therapy and contingency management (learning through systematic reward) are most effective. In addition, family therapeutic interventions have proven effective in children and adolescents. The abstinence rates are between 10 and 50%. About half of these patients will relapse within a year of treatment.

More lasting than trying to induce cannabis abstinence are improvements in the frequency and severity of cannabis use, associated psychosocial problems, and other health disorders associated with cannabis use. Internet and computer-based interventions are effective in reaching young people at the onset of problematic cannabis use and in reducing their use.

Medicines have not yet been approved for the treatment of cannabis-related disorders. Medication is only required if symptoms of withdrawal are severe.


The use of cannabis is widespread in the population and ranges from experimental to dependent use. Empirically, it has now been very well proven that biographically earlier, high-dose, long-term and regular use of cannabis increases the risk of various disorders of mental and physical health and age-appropriate development. In many studies, confounding variables were only insufficiently controlled, so that the question of a causal relationship between patterns of cannabis use and cognitive damage or the development of comorbid psychological or physical disorders cannot yet be answered conclusively. The global increase in THC levels in cannabis products may increase health risks, especially if cannabis is consumed in adolescence. Further research should clarify why some people are more affected and others less affected by the adverse effects. ■

Address for the authors

Dr. rer. nat. Eva Hoch

Clinic for Dependent Behavior and Addiction Medicine

Central Institute for Mental Health, Mannheim

[email protected]

@ Long version and literature on the Internet: