Our rating
 No smiley: On the available evidence, this treatment does not seem to be effective.


The rating system

  • 3 smiliesThese treatments are very useful. They are strongly supported as effective by scientific evidence.
  • 2 smiliesThese treatments are useful. They are supported by scientific evidence as effective, but the evidence is not as strong.
  • 1 smileyThese treatments are promising and may be useful. They have some evidence to support them, but more evidence is needed to be sure they work.
  • No smiley On the available evidence, these treatments do not seem to be effective.
  • Question markThese treatments have not been properly researched. It is not possible to say whether they are useful or not.
  • Exclamation MarkSafety or other concerns have been raised for the use of these treatments.

What is it?

Cannabis, also known as marijuana or weed, is a plant used as a recreational drug. Cannabis is commonly smoked, and can also be made into edible products or used to make oils. Synthetic versions of the chemicals found in cannabis can also be made in a laboratory.

How does it work?

Cannabis contains many compounds which can influence the chemical activity in the brain. The most well known are tetrahydrocannabinol (THC) and cannabidiol (CBD). It is unclear how these chemicals might help depression.

Is it effective?

Very few scientific studies have been conducted on the use of cannabis as a treatment for depression. One study treated a small sample of participants who had depression with synthetic THC. No improvements in mood were found, and some participants had to exit the trial early due to severe side effects.

Several studies have found that, in people who used cannabis, those who reduced their use actually experienced an improvement in their depression symptoms.

Research has also looked for links between cannabis use and depression in large groups of people. Large studies have found that cannabis use may be a risk factor for developing depression.

Are there any disadvantages?

Cannabis use is associated with a number of harmful effects. Cannabis can cause respiratory damage and illness (such as asthma, emphysema and lung cancer) if smoked, with this risk increasing if it is used over long periods of time. Cannabis can also cause drowsiness, memory impairments, nausea, dizziness and a lack of motivation. Even in smaller quantities, cannabis can affect driving skills and the ability to do other tasks (for example, perform duties at work). Some people may also experience anxiety and paranoia after using cannabis, which can be severe and very unpleasant.

Where do you get it?

Cannabis is illegal under Commonwealth law in Australia. The laws and penalties regarding the possession and use of cannabis vary from state to state. In some countries it is legal to use cannabis for either recreational or medicinal reasons.


Given the lack of evidence on cannabis, and its status in Australia as an illegal drug, it cannot be recommended as a treatment for depression.

Key references

  • Kotin, J., Post, R. M., & Goodwin, F. K. Δ9-tetrahydrocannabinol in depressed patients. Archives of General Psychiatry. 1973; 28(3):345-348.
  • Langlois C, Potvin S, Khullar A, Tourjman SV. Down and High: Reflections Regarding Depression and Cannabis. Frontiers in Psychiatry. 2021; 12:625158-.
  • Onaemo VN, Fawehinmi TO, D'Arcy C. Comorbid Cannabis Use Disorder with Major Depression and Generalized Anxiety Disorder: A Systematic Review with Meta-analysis of Nationally Representative Epidemiological Surveys. Journal of Affective Disorders. 2021; 281:467-75.
  • Sarris J, Sinclair J, Karamacoska D, Davidson M, Firth J. Medicinal cannabis for psychiatric disorders: a clinically-focused systematic review. BMC Psychiatry. 2020; 20(1):24-.

Last reviewed and updated: 21 August 2023