Developmental changes in best friendship quality during emerging adulthood

The purpose of this study was to examine change in four features of best friendship quality (intimacy, companionship, reliable alliance and conflict) from age 19 to 30 by gender and investment in romantic life. To this end, 363 participants (58% women) were asked about the quality of the relationship with their best friend and their level of investment in romantic life at ages 19, 20, 21, 22, 25 and 30. Latent growth curve analysis revealed a slight increase in reliable alliance and companionship and a slight decrease in intimacy in the early 20s followed by a steeper drop for these three features (quadratic trajectories), while conflict declined linearly. Women reported higher levels of intimacy and companionship and less conflict than men did at 19 years old. Also, their intimacy diminished throughout their 20s, slightly at first but more strongly thereafter. For men, it was lower early on and remained stable afterwards. Finally, investment in romantic life at age 19 was associated with change in intimacy levels shared with their best friend. This study confirms that features of best friendship quality change differently from one another during emerging adulthood and demonstrates the influence of gender and investment in romantic life on these changes.