Lynn,
I can relate greatly with your friend. I have found that my AD's don't make me happy - they make me not sad. I feel neutral and very rarely am I overly excited/happy/enthusiastic about anything. I'm sure different meds affect people in different ways and your friend could explain how he's feeling to his doctor.
Also, I went through extreme highs and lows which I rarely get anymore because of my AD's. These are not natural as it's a part of being manic. The AD's might be helping your friend and he's not experiencing these extreme highs or lows anymore. This is why he thinks life is boring or dull.
Hope this helps a bit... I'm not an expert!
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