The National Health Service (NHS) of the United Kingdom stated in a July 15, 2011 article titled "Does Cannabis Interact with Antidepressants or Lithium?" and posted on its website:

“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.

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.

Both TCAs [Tricyclic antidepressants] and cannabis can cause tachycardia and hypertension. 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.”

July 15, 2011