Loneliness has been defined as a 'sad subjective state resulting from dissatisfaction with one's social experiences'. However, whereas some children seem to enjoy playing alone and do not feel lonely when doing so others may experience loneliness even when they are in a room full of other children. There is a growing body of evidence linking loneliness to psychological problems and from middle to late childhood loneliness appears to be a marker for problems such as anxiety, low self-esteem and aggression. In adolescence and adulthood loneliness becomes increasingly associated with social anxiety and depression as well as obesity and alcoholism. A Canadian study of 139 5-6 year-olds looked at loneliness and its effects in this age group which has had little research so far. The researchers found that loneliness was associated with anxiety, aggression and peer exclusion. There was a difference between the children who were able to play happily by themselves and those who were reticent, spending their time watching other children without joining in and staring into space. Interestingly boys suffered more from loneliness than girls ; perhaps because it is seen as less socially acceptable for boys to be shy than girls.
Coplan, Robert J., Closson, Leanna M. and Arbeau, Kimberley A. - Gender differences in the behavioral associates of loneliness and social dissatisfaction in kindergarten Journal of Child Psychology and Psychiatry October 2007 48 (10), 988-995