A 2014 research review found that some adults with ADHD tend to be more likely to experience substance misuse as compared to others without ADHD. Some examples of substances that are misused or even abused include tobacco, alcohol or recreational drugs. Although the research isn’t clear on what the actual link between ADHD and substance abuse is, what was seen is that those with ADHD often use these substances as ways to self-medicate, believing that it will help them improve their sleep, focus, and relieve feelings of anxiety.