I am also experience hair thinning while on Wellbutrin. I have had blood tests and there is no other detectable cause. The dermatologist said that she was only able to diagnose as possibly hereditary. However, I began noticing it shortly after starting 300mg of Well XL and then noticed increased thinning when I went up to 450mg. I don't take any other medications at all.
I searched the Wellbutrin prescribing information (a pdf on the official Wellbutrin website) and this is all I can find:
Other Events Observed During the Clinical Development and Postmarketing Experience of Buproprion
[...]
Adverse events for which frequencies are not provided occurred in clincial trials or postmarketing experience with bupropion. Only those adverse events not previously listed for sustained-release bupropion are included. The extent to which these events may be associated with Wellbutrin XL is unknown.
[...]
Skin: Rare was maculopauplar rash. Also observed were alopecia, angioedeme, exfoliative dermatitis and hirsutism.
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Alopecia is hair loss. All that means is it was reported and they didn't do a study that would have produced data with which they could measure the likelihood that it is a Wellbutrin side effect. In other words, people said they were experiencing it but they can't confirm it.
I just dropped down to 300 mg and I'm contacting my shrink about tapering off completely - I feel like dealing with scalp showing through and feeling horribly self-conscious and unattractive because of it is not going to help my depression and self-esteem issues any.
I'm a woman by the way - the number of reports of hair thinning in women seems significant to me. I have no family history of thin hair on the female side that I know of.