I know a lot of people just swear by the meds, and others find side effects and personality changes like you did. I think it's very individual, and varies by the medication as well as by the child and the severity/specifics of the disorder.
Sometimes you find terrific doctors who are willing to look at a variety of approaches, and sometimes you find a doctor with a definite leaning toward a particular medication. Sometimes that's based on knowledge and experience, and sometimes (unfortunately) it's based on which drug company's rep visits the most and gives the most samples.
I also think there's tremendous value to looking at natural solutions and nutritional supplementation. I've seen incredible changes in kids and adults with focus issues, with or without hyperactivity, as also all kinds of kids on the autism spectrum and with sensory processing issues. There is a lot of research that has been done over the past 15 years with some food-based discoveries, and there have been many academics papers as well as support group validation and anecdotal info.
I agree that taking kids off processed foods can make a huge difference, as can eliminating dyes and GMO foods. Unfortunately, it can be difficult to do this unless you are an expert at reading labels (including the terms that cover up the additive's origin). The US requires very little in terms of labeling for GMOs though, so it's almost impossible to identify them. It's not enough to just serve fresh foods either.
I completely disagree with advice that says to go get this vitamin or that mineral. Once you start picking and choosing nutrients, you get into a level of science that most of us are not experience in. It absolutely flies in the face of nutrition and food science to start mixing & matching a few ingredients like calcium and B complex and magnesium. It's ineffective, expensive, and can be dangerous. I do not recommend it at all. Comprehensive supplementation is advised by all reputable food scientists and also the American Medical Association. The vast majority of children's vitamins even carry warning labels (like "keep out of reach of children) and also contain aspartame, sorbitol, dyes, and other questionable ingredients). It's a big business but it's based on profits and not kids' health. There is no science I'm aware of that supports it. Most doctors and nutritionists call this type of piecemeal approach either "expensive urine" because it's all eliminated, or "kitchen chemistry" because it's so haphazard. Think of all the "vitamin waters" that have different flavors based on what vitamins are included. WHAT? On what basis does that make any sense at all?
I think you have to make some choices based on your overriding philosophy, your willingness to get educated and give something else a good try (consistency is important no matter what route you choose), and your previous experience. But there's a lot of new information and you don't only have to go to medical conferences to get it.