Drug abuse is a universal problem. Wealth and status provide some measure of protection; rich white people are much more leniently treated by the justice system than poor addicts, especially of color. The jail sentences for users and peddlers of upscale drugs are much less severe, whereas cheap drugs that are a larger problem amongst the poor carry at times life sentences. Wealthy celebrity status protects addicts from the law, making the universal problem worse.
Drug abuse is something that can be influenced by many different aspects in our life. However, most people don't understand that. Being a celebrity and or wealthy can impact the amount of intention they get so sometimes it can be traumatizing which potentially leads up to drug usage and such.
With great wealth comes great access to luxury and indulgence. The wealthy elite have the time, money, and resources available to procure and use substances to excess. Their celebrity status may also protect them from legal consequences that a middle or working class individual would be penalized with, increasing the risk of substance abuse. Celebrities and the wealthy often have much pressure on them to perform and live in a certain way, and every move and personal issue can be publicized globally, and scrutinized by millions; to live with this increased level of pressure and expectations would surely drive anyone to self-medicate and soothe themselves with alcohol and/or drugs.
I believe that though many non-celebrities suffer from substance abuse (and we do not hear bout them because they are not celebrities), the lifestyle that money and fame supports is unfortunately one that can steer people towards substance abuse. The availability to the substance from the wealth and the stress from celebrity status both contribute.
Many, but not all, celebrities have to meet a lot of high expectations of them and there is pressure to deliver what their fans want. With busy lifestyles, it can become quite stressful. Drugs are often a way to escape that reality or maybe feel in control of their own lives.