Most people, when they think about commitment issues, immediately think of people who are in a relationship and can't settle down with one person. While this is true there are also many other aspects of commitment issues. What it boils down to is the fact that you can't decide on a choice that will affect you for a long period of time, whether it be 3 months, 5 years, or indefinitely. Which is why most people automatically link commitment issues to relationships, because most commitment phobic people run at the idea of marriage to somebody.
It's not because they don't love them or cherish them, but it's because their mind is nagging them about if this is the choice that they want to make for the rest of their life. Then they consider all of the alternate possibilities and try to confirm whether this truly is the best choice. So the best thing to do when they are stressing out like that is just sit them down and talk about how they are feeling and comfort them, but don't make them feel like they are being crazy because that will just make things 100% worse.
However, issues with commitment can start long before you are ready to date, as a child I found it hard to stay in activities for a long period of time and would often get stressed out. I would do activities for a couple of months to a year, but then I would quickly get bored and I would feel myself distancing from the group. It was because I wanted my freedom and the ability to do what I wanted to do when I wanted to do it, and I know that might sound insanely selfish, but sometimes you have to put yourself first. I'm a bird and you can't keep me in a cage, I have to be able to fly around and experience the world and not just limit myself to one thing.
Furthermore, I think my commitment problems will always affect my relationships, friendly and otherwise. Whenever I get close to people I always think in the long run, whether they are going to be there for me or not. If I feel like this person has no future in my life I will shut them out. That doesn't mean that I won't be friendly, but I won't let you in on my life. My loyalty will be absent because why waste my time on something that won't work in the long-run? However, once I feel like you are going to be steady in my life, I will devote myself to you and your happiness and my fears of commitment will subside. You just have to be patient with me until then. There will be times when I will still want my freedom and time to myself because I am very independent, but when you need me I will be there.