Other risks of regularly using cannabis can include:
Regularly using tobacco also increases the risk of tobacco-related diseases such as cancer and coronary heart disease.
If regular users stop taking cannabis, they may get withdrawal symptoms, such as feeling moody and irritable, feeling sick, difficulty sleeping, difficulty eating, sweating, shaking and diarrhoea.
Cannabis and mental health
Cannabis use may affect fertility. Regular or heavy cannabis use has been linked to changes in the female menstrual cycle and lower sperm count, or lower sperm quality in men.
It's possible to get addicted to cannabis, especially people who are considered regular or heavy users.
Regularly smoking cannabis with tobacco increases the risk of a baby being born small or premature.
The risk of developing a psychotic illness is higher in people who:
In general, all side effects will slowly decrease and then disappear within a few hours. This depends upon the dose taken and mode of administration.
A review of the effects of the medicinal use of cannabinoids indicated that the most frequent categories of adverse effects relate to respiratory, gastrointestinal, and nervous system disruptions. The common acute side effects of high doses of cannabis occur quickly after consumption, including:
Side effects and risks: quality is vital
The consumption of medicinal cannabis has not been shown to lead to life threatening adverse events, even at very high doses. However, an overdose of cannabis (THC) can result in a range of adverse effects, with high variability in tolerance between subjects. The most common adverse effect of overdosing a single dose of THC is anxiety, which, in some cases, may lead to mild acute psychotic states (panic attacks). In addition, increased heart rate and changes in blood pressure may occur.
On rare occasions, cannabis use can induce a state of psychosis in individuals with a genetic predisposition. As a result, patients with a (family) history of psychotic disorders, particularly schizophrenia and bipolar disorder, should be under careful psychiatric monitoring when using medicinal cannabis. Moreover, a short, acute psychotic like episode (involving anxiety and catastrophic thinking) is possible in the case of non-predisposed individuals, especially when very high doses of THC is taken.
Most unwanted side effects from the administration of medicinal cannabis may be prevented by adopting the following guidelines:
Long-term marijuana use has been linked to mental illness in some people, such as:
THC acts on specific brain cell receptors that ordinarily react to natural THC-like chemicals. These natural chemicals play a role in normal brain development and function.
Many people who use marijuana long term and are trying to quit report mild withdrawal symptoms that make quitting difficult. These include:
Are there effects of inhaling secondhand marijuana smoke?
Marijuana over activates parts of the brain that contain the highest number of these receptors. This causes the “high” that people feel. Other effects include:
While a psychotic reaction can occur following any method of use, emergency room responders have seen an increasing number of cases involving marijuana edibles. Some people (especially preteens and teens) who know very little about edibles don’t realize that it takes longer for the body to feel marijuana’s effects when eaten rather than smoked. So they consume more of the edible, trying to get high faster or thinking they haven’t taken enough. In addition, some babies and toddlers have been seriously ill after ingesting marijuana or marijuana edibles left around the house.
In another recent study on twins, those who used marijuana showed a significant decline in general knowledge and in verbal ability (equivalent to 4 IQ points) between the preteen years and early adulthood, but no predictable difference was found between twins when one used marijuana and the other didn’t. This suggests that the IQ decline in marijuana users may be caused by something other than marijuana, such as shared familial factors (e.g., genetics, family environment). 6 NIDA’s Adolescent Brain Cognitive Development (ABCD) study, a major longitudinal study, is tracking a large sample of young Americans from late childhood to early adulthood to help clarify how and to what extent marijuana and other substances, alone and in combination, affect adolescent brain development. Read more about the ABCD study on our Longitudinal Study of Adolescent Brain and Cognitive Development (ABCD Study) webpage.
Marijuana use has also been linked to other mental health problems, such as depression, anxiety, and suicidal thoughts among teens. However, study findings have been mixed.