They have to deal with problems that he is too immature to handle, or worries about problems, which are problems at all. Many kids drink to make them feel older and mature. It makes you more confident and sociable. Another cause of teenage drinking is escape from stress of school if they are overwhelmed with work or that they get really worried over slipping grades and that they just need to relax. Drinking will only make things worse.
Many teens drink because of peer pressure or just to fit in.
Kids may think that if they drink then they will fit in with the crowd and become more popular. Kids spend most of their spare time partying. The kid who doesn't take something to drink has a dozen friends all over him. Teens drink for the effect. To get high, to rebel, to alter their feelings of their environment, if only temporary.