L-shaped association between depressive symptoms and the number of close friends: A cross-sectional study

ObjectiveDepressive symptoms are a common disorder influenced by various factors, including genetic, environmental, and psychosocial aspects. This study aimed to explore the association between depressive symptoms and the number of close friends.MethodsThis cross-sectional study employed data from the 2005-2008 National Health and Nutrition Examination Survey. Weighted logistic regression was used to analyze the relationship between the number of close friends and depressive symptoms, and restricted cubic spline plots were constructed. Subgroup and sensitivity analyses were also performed.ResultsThis study included 5564 participants. After grouping participants based on the number of close friends into tertiles, a negative association was found between the number of close friends and depressive symptoms. After adjustment, the group with a higher number of close friends exhibited a 48% lower risk of depressive symptoms. An approximately L-shaped relationship was observed (nonlinear P = 0.001). Depressive symptoms decreased with an increasing number of close friends up to 10, beyond which the association plateaued.ConclusionAn approximately L-shaped relationship exists between the number of close friends and depressive symptoms. When the number of close friends was ≤10, a higher number of close friends was associated with a lower level of depressive symptoms.