Exploring like-attracts-like friendships in diagnosed and self-diagnosed populations: a description of 2 systematic reviews.

Introduction: Homophilic selection is the tendency for an individual to affiliate with and befriend peers who initially are similar to themselves on a variety of behavioral and physical characteristics [1]. This paper presents 2 systematic reviews exploring homophilic (friendship) selection: amongst individuals with a diagnosed psychiatric condition, and amongst individuals who self-diagnose. Both reviews aim to identify existing literature on the subject and to argue in support of further research in this area.

Methods: The first review, 'Do individuals with a diagnosed psychiatric condition exhibit homophilic friendship selection?', began with a two-wave database search of PsycINFO, Medline, and Embase from December 7th 2023 to August 7th 2024 via Ovid. A citation search of the accepted papers conducted independently by 3 authors produced 17 papers out of 24,546 screened against a detailed eligibility criteria.

Results and conlusion: Publications studying depression observed homophilic selection reliably (12,642 participants across 12 papers were recruited to investigate homophilic selection and depression). However, conditions like anxiety were largely exempt from investigation, as was the consideration of ethnic background and age, which is discussed to be an oversight.

Methods and results: The second review, 'Do individuals with a self-diagnosed psychiatric condition exhibit homophilic friendship selection?', was conducted via the same method on August 8th 2024 to produce no papers fulfilling the single eligibility criterion 'any friendship behaviour in individuals with a self-diagnosed mental illness'.

Conclusion: There is a complete absence of research into the friendship behaviours of the self-diagnosing mental health population. Given the increasing number of individuals across psychiatric conditions who currently self-diagnose, such research has a considerable academic and clinical value, which is discussed.