I advise you to talk with your teathers first and ask them to persuade your parents. You can recommend them to view on the following website:

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Mitimins. Although natural substances can help with mild cases of depression and other slight aliments, it has no effect on helping someone that is bipolar. This is a major chemical imbalance in the brain that at this time has to be treated with chemicals.

Fugly: I would go and see your counselor at school. This way you have someone to talk to that is accessible immediately. Explain to him/her your concerns and have them talk to your parents. Good luck, I hope you get the help you need.