I have gone through your query and understood your concern.
One common side effect of your drugs ,Zyprexa(Olanzapine
) and mirtazipe(mirtrazapine) is weight gain.You have not this problem,so these drugs and not the culpit of your weight problem.
At the other side,it is true that consuming lots of marijuana can cause weight loss
and supress appetite.So my advice is to reduce gradually and possibly to stop smoking
marijuana if you want to gain weight.
You didn't mention what's your thyroid diagnose.
Anyway i can say that Hyperthyroidism
can be a potential cause of your weight loss.For this reason i sugget to do the thyroid function test(TSH
,free T3 and freeT4 to see your actual thyroid function and to understand if your thyroid gland is the cause of weight loss.
If the test results will show hyperthyroidism,in this case you need to start the treatement and than gradually you will start to gain weight.
Hope i have answered to your question.If you have other queries,feel free and ask.I will be happy to help.