Cannabis

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

What does this rating mean?

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.
  • These treatments are not recommended and could be dangerousSafety 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?

Due to its status as an illegal drug in most countries, 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.

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. There are currently some clinical trials underway in Australia (and overseas) looking at the potential medicinal uses for cannabis, however it is not currently being researched as a treatment for depression.

Recommendation

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. (1973). Δ9-tetrahydrocannabinol in depressed patients. Archives of General Psychiatry, 28(3), 345-348.

Last reviewed and updated: 1 November 2019