During adolescence and emerging adulthood, the emotional centre of people’s lives shift from their immediate families to people outside of the family (i.e. friends). Friends provide a bridge between the close attachment to family members and the close attachments of a romantic partner.

Peers refer to people who have certain aspects of their status in common (e.g. both playing the same sport; both approximately the same age). Peers become more important during adolescence across cultures, although gender differences in adolescent relationships are more pronounced in traditional cultures. However, compared to Western culture, more time is spent with the family.

In adolescence, time spent with same-sex friends remains stable and time with other-sex friends increases. The relationships with family and friends during adolescence change in both quantity and quality. Adolescents start to depend more on friends than on parents or siblings for companionship and intimacy. Parents are preferred to discuss topics related to education and future occupation but friends are preferred for personal topics.

The direct influence of parents decreases during adolescence but parents shape adolescent peer relationships in indirect ways by influencing their social network (e.g. choice of residence; school) (1), encouraging or discouraging contact with some peers (2) and through their parenting practices (3).

Adolescents typically feel happier with friends than with family because friends mirror emotions and because they feel free and open with friends that they rarely do with parents. Adolescents’ attachment to friends and their strong reliance on friends leave them vulnerable emotionally (e.g. a lot of worry about whether they are liked).

Intimacy refers to the degree to which two people share personal knowledge, thoughts and feelings. Adolescent friendships are characterized by intimacy more than friendships in childhood. The need for intimacy with friends intensifies in early adolescence. This is partly due to increases in capabilities for perspective taking and empathy. Friends promote further enhancement of perspective taking because they share their thoughts. Adolescents find trust (1), loyalty (2) and intimacy (3) more important in friendships as compared to younger children who are focused on shared activities (e.g. baseball). Self-disclosure promoted emotional closeness for young women whereas shared activities where usually the basis of feeling emotional closeness in young men.

Adolescents’ greater abilities for abstract thinking makes it possible for adolescents to think about and talk about more abstract qualities in their relationships. Adolescents also have a greater ability for complex thinking and this allows them to discuss the complexities of social relationships. Talking about these social cognitive topics promotes the kind of exchange of personal knowledge and perspectives that constitutes intimacy.

There are consistent gender differences in the intimacy of adolescent friendships. Girls tend to have more intimate friendships than boys (1), girls spend more time than boys talking to their friends (2), they place a higher value on talking together as a component of their friendship (3), they rate their friendships as higher in affection, helpfulness and nurturance (4) and they are more likely to say they trust and feel close to friends. Boys are more likely to emphasize shared activities as the basis of friendships. This may be due to the fact that puberty emphasizes gender more and intimacy is associated with being female. Boys may thus refrain from intimacy.

Friendships may change in emerging adulthood compared to adolescence:

• Emerging adults typically leave home and this may increase the importance of friendships.
• Intimacy becomes more important.
• Emerging adults are more likely to have other-sex friendships.
• The importance of friendships tends to decline as romantic relationships develop.

Similarity is one of the key reasons why people become friends (e.g. similarity in attitude; style; music). Similarity in ethnicity predicts friendships in adolescence but not in childhood. Similarity in risk behaviour is important as well.

Friends’ influence refers to the influence friends exert on a person. Friends have substantial influence on adolescents while the effect of the entire peer group is weak. Friends can encourage or discourage certain activities. The strength of friends’ influence increases in early adolescence, peaks in the mid-teens and declines in late adolescence. The relationship between friends’ risk behaviour and own risk behaviour may exist because of selecting friends based on similarity. Friends tend to become more similar over time and this also holds for risk behaviour.

According to Sullivan, friendships are important in adolescence for building self-esteem and it helps them develop social understanding. There are four types of support that friends may provide to each other in adolescence:

1. Information support
   This refers to advice and guidance in solving personal problems.
2. Instrumental support
   This refers to help with various tasks.
3. Companionship support
   This refers to relying on each other in social activities.
4. Esteem support
   This refers to support for self-esteem (e.g. encourage or console a person).

Supportive friendships lead to higher self-esteem and lower depressive symptoms and are associated with improvements in academic performance. Supportive friendships can both increase or decrease risk behaviour.

Cliques refer to small groups of friends who know each other well. They form a regular social group. The size range is between 3 and 12. People in a clique know each other well and it can be defined by distinctive shared activities. Crowds refer to larger, reputation-based groups of adolescents who are not necessarily friends and do not necessarily spend much time together. There are five types of crowds:

1. Elites (i.e. populars)
   This refers to people with the highest social status in the school.
2. Athletes
   This refers to sports-oriented students.
3. Academics
   This refers to people striving for good grades.
4. Deviants
   This refers to people who are alienated from the school social environment.
5. Others
   This refers to students who do not stand out in any particular way.

Within crowds, there are cliques and close friends. Crowds serve the function of helping adolescents locate themselves and others within a school social structure. It helps them define their own identities and the identities of others.

Sarcasm and ridicule play a part in adolescent friendships and clique interactions. Antagonistic interactions refer to interactions which are directed at members within the group and those outside of the group and include sarcasm and ridicule. This may promote the establishment of a dominance hierarchy and it may reinforce clique conformity.

Relational aggression refers to a form of non-physical aggression that harms others by damaging their relationships (e.g. excluding them; spreading rumours). It includes sarcasm (1), ridicule (2), gossiping (3), spreading rumours (4) and exclusion (5). Relational aggression is more common among girls while physical aggression is more common among boys. This may be due to the different gender roles. Peers and crowds become more important due to school as adolescents spend a lot of their time with peers.

Crowds become more differentiated in mid-adolescence and become more central to adolescents’ thinking about their social world. The influence of crowds diminishes in late adolescence. Crowd development parallels the course of identity development.

There are five stages of clique development:

1. Stage 1
   Here, adolescent social lives mostly take place within the same-sex cliques.
2. Stage 2
   In this stage, mixed-sex cliques become more common.
3. Stage 3
   In this stage, the gender divisions begin to break down as the clique leaders begin to form romantic relationships.
4. Stage 4
   In this stage, all cliques and crowds are mixed-gender groups.
5. Stage 5
   In this stage, the structure of cliques and crowds begin to break down as a result of romantic relationships.

However, this model may be relatively outdated.