Is there a chance my mother committed suicide?

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When i was 12 years old (i am 19 now) my mother passed away. For 7 years now everyone told me she overdosed on Prozac. Well they told me 3 weeks ago that she really died for alcohol and overdosed on meth. I really dont want to believe it was suicide. She had alot of problems and she was depressed. I did not live with her because she tried to commit suicide before. She has been got for 7 years now and i am still trying to find the answer. Could i please have someone's opinion on this? I know i will not find the answer here but i would like to know can you overdose on meth on purpose? Thank you in advance