Some small studies and anecdotal sources suggest that autistic people may benefit from the therapeutic effects of cannabis. However, there is currently not enough evidence to support this claim.

The brains of autistic people and people who do not have autism spectrum disorder (ASD) develop differently. As a result, autistic people may behave, interact, and learn differently from people without ASD.

Having ASD may lead to repetitive patterns of behavior and some difficulties in social interactions. ASD also sometimes causes delayed language development, hyperactivity, seizures, and gastrointestinal problems.

Medications can address some symptoms of ASD. Also, if ASD symptoms have negative effects on the quality of life, a person might consider trying medicinal cannabis.

Keep reading to learn more about ASD and cannabis use, including the risks, possible benefits, and some other alternative ways of reducing certain symptoms.

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Significant stigma surrounds autism. Generally, medical experts do not believe that there is a cure. And autistic people may feel that there is no need for treatment, management, or a cure.

Meanwhile, researchers continue to explore the therapeutic uses of cannabis. According to a 2018 review, there is conclusive evidence that cannabis can treat:

  • pain in adults
  • nausea and vomiting due to chemotherapy
  • muscle spasms and tightness connected with multiple sclerosis

The author of this review also found moderate evidence for:

  • secondary sleep disturbances

While this review did not mention ASD, research from 2019 analyzed existing peer-reviewed literature relating to cannabis as an ASD treatment. The authors concluded that there was a lack of clear evidence that cannabis reduced symptoms of ASD.

The team highlighted an urgent need for large-scale studies to improve understanding of the risks and possible benefits.

However, other studies and anecdotal accounts suggest that cannabis may benefit people with certain ASD symptoms. For example, authors of a 2021 review concluded that cannabis and natural compounds in the plant, called cannabinoids, could be effective alternative therapy for ASD symptoms.

The authors of the 2021 review found that cannabis products can reduce the frequency and intensity of a range of symptoms, including:

  • hyperactivity
  • attacks of self-mutilation and anger
  • sleep problems
  • anxiety
  • restlessness
  • psychomotor agitation, which involves activity without purpose, such as pacing the room or tapping the toes
  • irritability
  • aggressiveness
  • depression

They also found evidence that cannabis may improve:

  • cognition
  • sensitivity of the senses
  • attention
  • social interaction
  • language

Also in 2021, a researcher at Minnesota State University carried out a review of the scientific literature on autism and marijuana in children. The findings suggest that cannabis may help reduce the severity of symptoms involving:

  • social communication
  • self-injury
  • restlessness
  • rage attacks
  • agitation
  • aggressiveness
  • irritability

The researcher also found benefits for conditions that autistic children may also experience, including:

  • anxiety and nervousness
  • epilepsy
  • sleep problems
  • hyperactivity or concentration problems associated with attention deficit hyperactivity disorder

The treatment led to a reduced need for medication in some participants.

A 2019 study looked at the effects of cannabidiol (CBD) in 53 children with ASD. The children were, on average, 11 years old. Nurse practitioners taught the parents how to administer oral CBD oil. The children received the treatment for an average of 66 days.

The team found that almost 70% of the children who experienced rage attacks demonstrated an improvement in this symptom.

Similarly, around 70% of the children who experienced hyperactivity also showed improvements. And of the 21 children with sleep problems, over 70% showed improvement. Almost half of the 17 children with anxiety demonstrated a reduction following CBD use.

Most researchers agree that drawing clear conclusions about the effects of cannabis on ASD requires large-scale, high-quality clinical trials.

The studies above describe several common side effects of cannabis as an ASD treatment, most of which appear to be mild. The side effects include:

  • sleep disturbances
  • drowsiness
  • appetite changes
  • restlessness

The Minnesota State University study also noted one episode of psychosis, which required treatment.

In 2019, researchers analyzed reviews to assess the effects of medical cannabis. They found adverse effects in 49 out of 59, or 83%, of the reviews that had compared the effects of cannabis with those of a placebo. They found adverse effects in 20 out of 24, also 83%, of the reviews that had compared cannabis with active drugs.

More than half of the reviews reported minor side effects, such as drowsiness and dizziness. But 21 out of the 59 reviews that reported on adverse effects found serious harms.

It is worth noting that some reviews looked at synthetic cannabinoids, rather than compounds extracted from the plant. Research indicates that synthetic cannabinoids can have more serious side effects than plant-based cannabinoids.

Also, some researchers caution that taking cannabis may have long-term effects that experts do not yet fully understand.

A multicenter survey suggests that 44.8% of autistic adults in Germany currently use or have used complementary and alternative medicine (CAM).

Some examples of CAM to treat symptoms of autism include:

  • homeopathy
  • acupuncture
  • yoga
  • biofeedback
  • animal-assisted therapy

However, while these therapies are unlikely to have serious side effects, little scientific evidence suggests that they treat ASD symptoms.

There is, however, some evidence that nutritional changes may help. For example, a 2019 study found that taking daily omega-3 long-chain polyunsaturated fatty acids might improve some ASD symptoms. The participants received 722 milligrams of docosahexaenoic acid with or without 2,000 international units of vitamin D3. This study involved 73 autistic children aged 2.5 to 8 years in New Zealand.

Some people also consider chelation therapy, a procedure to remove heavy metals from the body, as a treatment for some symptoms of ASD.

While a 2017 study suggests that there may be a connection between toxic metal uptake, essential element deficiency, and ASD risk and severity, there is little evidence that chelation therapy is safe or effective in this context. It has the potential to cause serious harm, including calcium deficiency, kidney damage, and death.

Some research suggests that cannabis may help treat certain ASD symptoms in some people, though there are risks. Overall, drawing conclusions requires more high-quality clinical studies.

People also consider a range of other alternative therapies, though most have little scientific backing.