There are certain causes of depression in teenagers. For instance, the main causes that teenagers may suffer from depression are academic stress, problems at home and at school (Vidyarthi, K., 2015). Causing the depression by financial struggles in family, having low self-esteem, lacking the ability to face the difficulties is possible (Vidyarthi, K., 2015). No doubt the academic stress will bring about depression suffered from teenagers. Compare with the pass, social competition has been more fierce nowadays. Teenagers are one of the casualty of this problem. There is a possibility that teens will be thought they are not competitive enough lead to feeling stressful. Moreover, teenagers may feel stressed as a result of the parents are having the greatest expectation of children’s’ achievement. The parents may want them to take part in several extra-curriculum class such as Mathematical Olympiad classes after school. They may feel stressed due to they don’t have enough resting time for recreation. There are some problems at home of teenagers. Consequently, they may feel sulk. For instance, divorcing parents may cause the depression to teenagers. It will lead to emotional disturbance of teens due to facing the dissolution family such as confronting their parents are quarrelling with each other will lead to feeling dismayed. In addition, teenagers are in the rebellious period, who may ignore or argue with their parent lead to having conflicts and a bad relationship. These will cause stressful for the teenagers. Nowadays, parents are having long working hours and do not take initiative to care about their children or communicate with them. Teens will consider their emotion and feeling are neglected by their parents lead to feeling lonely and neglect. In some extreme cases, teens may suffer from domestic violence lead to feel ashamed and become self-enclosed to protect themselves from harm.They may feel stressed due to they would not express their emotions and feel no one they can talk with and understand them. Teens may also have problems at school lead to suffer from depression. The targets of the abuse tend to teenagers who are different to others. The act of the abuse is designed to induce the victims a sense of powerlessness and helplessness, who are forced to experience the painful stress and helpless that they cannot handle and ignore (Angela. O., 2010). Moreover, teens may not know how to avoid being bully. The bullies are based on the race, religious, physical disability and family background. There several shortcomings of teens being bully. For instance, there is a possibility that the teens will be engaged in self-annihilation behavior like drug abused or smoke. Low self-esteem is also a disadvantage of peer pressure owing to the alienation from the peers. They may think they are different from the others and cannot gain support from the peers. Those are the causes of depression in teenagers. It is shown that it is a very serious problem in Hong Kong.