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Does cannabis interact with antidepressants or lithium?

Posted by Be Well

Does cannabis interact with antidepressants or lithium?
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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:

  • Tricyclic 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.
  • Newer 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 depression.

Tachycardia (an abnormally fast heartbeat), dizziness, anxiety, drowsiness, 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 hallucinations.

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 SSRI 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 SSRI. Both SSRIs and cannabis are very widely used, and there is little evidence that people who use cannabis should normally not take SSRIs.

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 hallucinations.
  • There has not been any proper research on taking cannabis with SSRI 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 antidepressants.
  • There is little evidence that people who use cannabis should normally not take lithium, but again proper research is not available.

It's important to remember that anyone taking an antidepressant is being treated for a serious mental illness. Smoking weed can and will interfere with that treatment.

If someone is serious enough about seeking treatment, they need also to consider the lifestyle changes that will optimize that treatment.

 Cannabis use doesn't usually interfere with treatment, it is actually commonly used to compliment treatment and alleviate certain side effects cause by prescription medication.  Although unlikely, there are certain medications and treatment regimens that should not be combined with cannabis.  Talk to your doctor before modifying your treatment or beginning using cannabis.

NOTICE: The information provided on this site is not a substitute for professional medical advice, diagnosis, or treatment. Never delay or disregard seeking professional medical advice from your physician or other qualified health provider because of something you have read on Wellsphere. If you have a medical emergency, call your doctor or 911 immediately.
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