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It is very difficult to comment regarding his state without examining him and knowing the current medications he has been taking as any psychiatric patient needs a careful and thorough evaluation before being prescribed any medications.
Since he has bipolar mood swings are very common in it and you have to learn to deal with it.Calm him down and make him relaxed.He should feel comfortable and should confide everything to you.Since you are very close to him understand that he can behave like this.Ask him to reduce smoking and alcohol.
Consider visiting his treating Physician for examination.
Take Care!