What Causes Excessive Sleepiness While On Olanzapine?

Question: Hello sir.if u remember I had consulted u regarding my 20 year old son in XXXXXXX He was diagnosed as drug induced psychosis(marijuana) in January 2015 and was started on olanzapine 5mg to which he responded well.in may 2015 he started sleeping excessively often not getting up till late afternoon.otherwise he was fine.you advised us to reduce the dose of olanzapine to 2.5 mg in XXXXXXX as his increased sleep hours were interfering with his daily routine. So the dose was reduced to 2.5mg after consulting my son's consultant.the sleep pattern improved after some days..rest all remained fine.so till now he has taken olanzapine 5mg for 5 months and then 2.5 mg for 4 months and 15 days..he is completely fine(as it appears to us from his daily behaviour although if we ask him if he has any problem he closes up.)he is now studying well for approximately 10 hours a day.he regularly attends his civil services coaching class 3.5 hours a day with religious punctualityand sincerity.he interacts with all relatives who come to our house with confidence and politeness.he has weekly interaction with his friends however he is more focused towards passing upsc .he reads the newspaper,editorials daily and watches both educative television programs as well as entertainment program of his choice during his off time.He has chosen this path on his own without any pressure from our side and his academic performance in test series is much above our expectations and very promising.he is a happy 20 year old with a goal in life towards which he is working..the main concern for this consult is that we do not want any relapse and that the excellent results achieved should remain.in light of the above mentioned facts please advise how long the treatment has to be continued and when can be safely stopped. is there any chance of relapse after discontinuing therapy..he is off marijuana since last October .Sir do u have record of our previous conversation or do u need me to send u the whole information again.he most probably abused marijuana for approximately 7-8 months in 2014 after he was first exposed to it in university.in October 2014 we shifted him back home.

Sir thanks for ur valuable consult.I have a few queries.firstly that he is eligible to appear for upsc in 2017 Dec.that's 2years from today.so what should be my approach considering this.but these years are very crucial to his preparation.he however would be giving a dummy attempt next year.is it advisable to continue the meds for this long..do I need to get any investigations done to look for some side effects of the drug..secondly if I taper his dose what kind of problem can occur and u mentioned that if he has any problem for more than three days I should again hike the dose.do u mean that after reducing the dose if he faces any of the old symptoms for more three consecutive days or more than three random days...what is the maximum and minimum time after dose reduction when reversal or aggravation of situation can occur.can failure lead to a relapse although we are very supportive and motivate him and regularly counsel him for any such eventuality