Most people feel lonely sometimes,but it usually only lasts between a few minutes and a few hours,This kind of loneliness is not serious.In fact,it is quite normal.For some people,though,loneliness can last for years.Now researchers say loneliness comes in three different types. The first kind of loneliness is temporary.This is the most common type.It usually disappears quickly and does not require any special attention.The second kind is situation,for example,family problem,the death of a loved one,or moving to a new place.Although this kind of loneliness can cause physical problems,such as headaches and sleeplessness,it usually does not last for more than a year.The third kind of loneliness is the most serious.Unlike the second type, chronic (the opposite of'temporary') usually lasts more than two years and has no specific cause.People who experience habitual loneliness have problems socializing and becoming close to others.Unfortunately,many chronically lonely people think there is little or nothing they can do to improve their condition. Psychologists  agree that one important factor in loneliness is a person's social contacts,for example,friends,family members,co-workers,etc.We depend on various people for different reasons.For instance.our family give us emotional support,our parents and teachers give us guidance, and our fiends share similar interests and activities. However,psychologists have found that, though lonely people may have many social contacts,they sometimes feel they should have more.They question their popularity. Psychologists are trying to find ways to help habitually lonely people for two reasons:they are unhappy and unable to socialize arid there is a connection between chronic loneliness and serious illness such as heart disease,while temporary and situational loneliness can be a sad,and sometimes dangerous condition. Loneliness is divided according to    _   .
the time it lasts the places where it appears different people it happen to different seasons when it appears