Children and adolescents who are exposed to victimization face increased risk of diverse negative outcomes by early adulthood (e.g. psychopathology; lower educational and career attainment; inflammatory disease). It could lead to loneliness, which refers to psychological distress associated with perceived shortcomings in one’s social relationships. Individuals vary in their susceptibility to feeling lonely. The heritability of loneliness is 40%-50%.

The evolutionary model of loneliness states that humans are motivated to seek social connection as it confers a sense of safety. Being victimized is a sign that one’s safety is compromised and this could elicit a feeling that one’s social network is deficient and not fulfilling the desired functions.

Bullying has several characteristics:

• It takes place between peers of similar age.
• It is characterized by an imbalance of power in favour of the perpetrator.
• It takes place online or offline (i.e. cyberbullying).

With cyberbullying, there is no physical location (1), the identity of the perpetrator may not be known (2) and it may continue even if the victim removes oneself from the situation (3). It is associated with greater loneliness and other emotional problems.

Bullying may play an important role in the development of loneliness. Emotional maltreatment may disrupt the formation of secure attachments and this negatively shapes individuals’ perceptions of their relationships with others. This could have a negative effect on loneliness. Polyvictimization refers to the experience of multiple victimization of different types. This is a stronger predictor of negative outcomes.

People that are victimized may be more lonely but it is also possible that more lonely people get victimized more often. This may be due to traits and negative stereotypes associated with loneliness (e.g. shyness).

People who have been exposed to one form of severe victimization are lonelier than those who are not. People who have been exposed to multiple forms of victimization are even more lonely. People who have been victimized in both childhood and adolescence were lonelier than people who were victimized in one of these time periods.

Bullying is associated with loneliness regardless of pre-existing psychopathology or genetics (i.e. it also is the case for twins). Adolescent victimization is associated with greater feelings of loneliness and especially for severe maltreatment (1), sexual victimization (2) and neglect (3) regardless of childhood loneliness or victimization.

Severe physical or sexual abuse and bullying up to age 12 predicts feelings of loneliness at age 18. This is mainly the case for frequent bullying, regardless of loneliness in childhood. Lonely children are at increased risk of experiencing new instances of victimization during adolescence.

The loneliness that victimized adults in childhood and adolescence felt is partly explained by the presence of mental health problems and by genetic influences. This holds for all forms of victimization except for bullying.

In late childhood and early adolescence, feelings of loneliness are strongly related to an unfulfilled need to be accepted by peers. Bullying by peers is a frustration of this need. However, bullying has an effect regardless of social exclusion. Being bullied while seeing other peers have normal relationships could elicit a sense of injustice and a perception of oneself as an outsider. This feeling of having no one to turn to for support could increase feelings of isolation and loneliness. Bullying could also increase loneliness through diminished self-esteem (1), social anxiety (2) and elevated sensitivity to social rejection (3).

Bullying is associated with loneliness in childhood via environmental factors. The more long-term association between childhood bullying and young adult loneliness is mediated by genetic factors. This means that it is possible that only those with genetic vulnerability continue to feel lonely over time.

Children exposed to physical and emotional abuse were lonelier at age 12 only if they exhibited symptoms of depression and anxiety. Parental antisocial behaviour or domestic violence in early childhood are not associated with loneliness in adulthood. Victimization within the family home seems more relevant for loneliness if it is experienced later in development (e.g. adolescence). The relationship between loneliness and sleep impairments in stronger in individuals with a history of physical maltreatment. The effect of victimization on loneliness may vary according to the developmental stage in which it is experienced.