Introduction

During the adolescence period, peers become increasingly important, adolescents also spend more and more of their time with their peers. This changed use of time entails a major disadvantage: the chance of rejection is increased. On the other hand, peers also offer benefits such as social support. This can then reinforce adolescents against rejection by others. The more social support an adolescent receives, the less adverse effects he or she experiences after being rejected by peers. The underlying mechanisms for this effect are still unknown.

The current study looks at the neurobiological background of friends during adolescence and rejection by peers at a later age. A recent idea is that people who receive more social support experience social stressors as less threatening.

The dorsal anterior cingulate cortex and the anterior insula are associated with the affective response to negative social experiences, such as social exclusion. With negative social interactions, people with many friends should, therefore, show less activity in these two structures. A recent study showed that young adults who have daily contact with close friends show less activity in the dorsal anterior cingulate cortex in social exclusion. The current study extends this finding to the question of whether social contacts during adolescence have the same effect when social exclusion only occurs later (in young adulthood).

Friendship during adolescence was measured in the current study as the amount of time the adolescent spends with friends (outside of school) using a diary. Two years later, the participants were examined with an fMRI scan while they were excluded by two peers. The prediction was that when adolescents spent many years with peers, they would be less sensitive to social exclusion in young adulthood.

Methods

Attendees

Research was conducted among 21 participants, 13 of whom were women. They were in the last year of their high school (12th grade). About half of the participants were white and the other half were Hispano.

Procedure

The participants had to fill in their diaries every evening for two weeks. In it, they stated the amount of time they had spent outside school with their friends. The fMRI scan was performed about two years later.

fMRI

Cyberball was used to create the illusion of social exclusion. The participant thinks that he is replacing a ball with two others that he had met before the fMRI scan (a man and a woman). The participant was able to decide for himself to whom he threw the ball, the decisions of the other two people were made by the computer. After the participant was involved in the first ten throws, he was excluded from possession for the rest of the game.

All participants also performed a control task prior to the Cyberball game. Hereby they looked at an asterisk (=star) that in a triangular form closely resembled the Cyberball game.

Analysis schedule

The Cyberball game and the control task were executed in a block design. Group contrasts were used to measure neural activity. This involved looking at neural activity during the period of exclusion during the Cyberball game and during the control task.

Regression analysis (Region of Interest, ROI) was used to measure the relationship between time spent with friends in adolescence and brain activity (dorsal anterior cingulate cortex and anterior insula) in social exclusion. In addition, a regression analysis was performed on the activity in the entire brain during the social exclusion and the time spent with friends in adolescence.

Results

Behavioural analysis

Adolescents spent 0 to 4.47 hours a day with their friends. There was no gender difference, but there was a difference in origin: white participants spent more time with friends than Hispanics. All statistical analyzes, therefore, checked for origin.

The main effect on the entire brain

During social exclusion, there was greater brain activity in the dorsal anterior cingulate cortex and the left and right anterior insula compared to the control condition. In addition, there was also increased activity in different brain areas involved in emotion regulation.

ROI

There appeared to be a negative relationship between the amount of time an adolescent spent with friends and the activity in the anterior insula during social exclusion (the more time spent with friends, the less activity in the anterior insula). No association was found with activity in the dorsal anterior cingulate cortex.

Whole brain

The relationship between friends in adolescence and reduced brain activity in young adulthood in social exclusion related only to two areas in the left anterior insula and an area just behind the dorsal anterior cingulate cortex, still associated with this structure, but not included in the ROI analysis. There appeared to be no effect on other brain regions.

Discussion

A larger amount of time spent with friends during adolescence appears to be related to a reduced sensitivity to social exclusion during young adulthood. This contributes to our knowledge about friendships during adolescence and their long-term effects. This finding also confirms results from previous research. For example, it has been shown that reduced pain-related neuronal reactions occur with social exclusion (adults) when there is a lot of contact with supportive others.

In addition to the above, the findings in the current study appear to be evidence of the protective effect of friends during adolescence in the long term. However, more research is needed here. The finding that friendship mediates the degree of social stress is also supported by current research.

However, the results of the current study are not entirely clear: friendship during adolescence, for example, could result in people becoming less sensitive to negative social events, rather than an improved ability to regulate affective responses to social stress.

Rejection by peers is less threatening for adolescents with many friends:

• They know they have reliable friends, so rejection by a peer is not a bad thing.

• They know they are accepted by many peers, so rejection is not threatening to this acceptance.

• Rejection increases the need to be in contact with someone. An adolescent with many friends has an increased chance of this.

• Friends who witness the rejection often help the adolescent.

Limitations and future research

This study looked at the amount of time an adolescent spent with peers. The same research could be performed with other variables, such as the number of friends or the quality of the friendship. In addition, stability could also be considered: can the adolescent maintain a friendship for a longer period of time and what effects does this have on social exclusion?

In the current study, it has been decided to measure the time spent with peers and social exclusion both at one time. The change in this over time could, therefore, be an interesting research topic.

In addition, the study did not look at current friendships either. It cannot, therefore, be stated with certainty that friendships in adolescence have achieved this effect; it could be that an adolescent who spends a lot of time with friends still does this in adulthood. Research that takes this into account is therefore desirable.

The two areas of the brain that were specifically investigated in the current study were selected on the basis of earlier research. However, this does not mean that only these brain regions are involved. The underlying mechanisms are also not disclosed.

Other biological and neurochemical mechanisms should also be further investigated.