If you have any concerns about the information below, or need any help understanding it and relating it to your own situation, talk to your doctor or pharmacist.
Cannabis or marijuana is usually smoked and typically mixed with tobacco.
There are four main groups of
antidepressants (TCAs) - for example, amitriptyline, imipramine, dothiepin.
- Selective serotonin reuptake inhibitors (
SSRIs) - for example, fluoxetine, sertraline, paroxetine, citalopram.
- Monoamine oxidase inhibitors (MAOIs) - for example, phenelzine.
antidepressants - mirtazapine, venlafaxine and reboxetine.
Lithium is used to treat bipolar disorder, a condition where people can switch between
depression and mania (extreme excitement and agitation).
It is not clear how often cannabis itself can cause
depression, but research suggests that this can happen. It is therefore recommended that if you are depressed, and you use cannabis regularly, you should try giving up and see if that helps. One small study suggests that a chemical in cannabis might cause severe
anxiety and unease in people with moderate to severe
Tachycardia (an abnormally fast heartbeat), dizziness,
nausea, vomiting, difficulty sleeping and confusion are all possible side effects of cannabis. These side effects can also be caused by certain
antidepressants, so using cannabis at the same time can make them worse.
Tricyclic antidepressants (TCAs)
Both TCAs and cannabis can cause tachycardia. There are seven published cases of healthy, young people, without a
heart condition, experiencing a dangerous effect by mixing TCAs and cannabis.
In five cases, the
heart was made to beat so fast that the people affected found it frightening. These cases were accompanied by other side effects such as confusion, restlessness, mood swings and
In one serious case, tachycardia was accompanied by tightness in the chest,
pain in the throat and extreme agitation, and emergency treatment was needed. This person had taken TCAs and smoked cannabis separately before without having a bad effect.
In another serious case, the tachycardia was so serious that treatment in intensive care was needed. This person had used cannabis before without problems and had even used small amounts without problems while taking a TCA. The tachycardia was probably triggered by smoking more than their normal amount of cannabis.
You should not smoke cannabis if you take TCAs because of these risks to your
heart. Either stop using cannabis or ask your doctor for an
antidepressant which appears to be a safer choice.
Selective Serotonin Reuptake Inhibitors (SSRIs)
A single report describes the
onset of mania in a person taking fluoxetine with cannabis. However, fluoxetine on its own may have caused this. There are no other reports of this happening with fluoxetine and cannabis, and no problems have been described between cannabis and any other
SSRIs and cannabis are very widely used, and there is little evidence that people who use cannabis should normally not take
Monoamine Oxidase Inhibitors (MAOIs)
Laboratory work suggests that cannabis might affect the way these medicines work. It is not clear what effect this may have on people, so MAOIs and cannabis should not be taken together.
Newer antidepressants such as mirtazapine, venlafaxine and reboxetine
There is no published research that has looked at taking these medicines and cannabis. However, they are too new to be sure and a problem might have been missed. Therefore the newer
antidepressants should not be taken with cannabis due to lack of information.
The combination of lithium and cannabis has not been studied in people. However, illegal drugs (including cannabis) are commonly taken by people with bipolar disorder, many of whom take lithium. In one reported case, a person had increased
blood levels of lithium while using cannabis, and this was linked to side effects. Although it is impossible to be sure, this may have been a coincidence because it has never been described again. There is little evidence that people who use cannabis should normally not take lithium.
- If you use cannabis regularly and are depressed, try stopping it to see if that makes you feel better.
- If you take cannabis with
antidepressants, they can produce similar side effects so be careful.
- Do not take cannabis with TCAs because this increases the risk of tachycardia and other side effects such as confusion, restlessness, mood swings and
- There has not been any proper research on taking cannabis with
antidepressants. However, the limited information available suggests that
SSRIs may be a safer choice of
antidepressant if you regularly use cannabis. Speak to your doctor.
- Do not take cannabis with MAOIs or newer
- There is little evidence that people who use cannabis should normally not take lithium, but again proper research is not available.