I have been vegetarian for years, there is no difference in side effects.
HOWEVER, that does NOT mean that diet can not effect symptoms. In fact, I have found that diet is the ONLY thing I can do to get rid of my insomnia and diminish the brain fog. I have tested this two ways; first, at the advice of someone on this website, I went COMPLETELY raw vegan (never cheated) for approximately 8 months. In the beginning, I avoided sugar for the most part as well. I ate mostly fat via nuts and avacados, and leafy greens. I did NOT feel better during this time. Eventually, I started eating very large quantities of fruit, and added quite a bit of natural sweets as well. My insomnia and brain fog DID improve at this point.
However, around this time, I got a stool culture which indicated a possible systemic fungal infection, so I immediately changed my diet to an “anti-candida diet.” I am not certain if I have candida (there is a blood test with results pending, hopefully get them today), but regardless, this diet is supposedly good for fungal infection in general. Immediately after switching to this new diet, my insomnia returned, and my mental sides got worse. There is no doubt that this was a result of changing my diet to one with very little sugar and mostly fat.
Personally, I believe at least part of the problem is fungal infection related, as taking 2 weeks of diflucan gave me notable improvement for a solid month.