title: Social isolation, loneliness and depression in young adulthood: a behavioural genetic analysis.
abstract: OBJECTIVE
  To investigate the association between social isolation and loneliness, how they relate to depression, and whether these associations are explained by genetic influences.
  
  
  METHODS
  We used data from the age-18 wave of the Environmental Risk Longitudinal Twin Study, a birth cohort of 1116 same-sex twin pairs born in England and Wales in 1994 and 1995. Participants reported on their levels of social isolation, loneliness and depressive symptoms. We conducted regression analyses to test the differential associations of isolation and loneliness with depression. Using the twin study design, we estimated the proportion of variance in each construct and their covariance that was accounted for by genetic and environmental factors.
  
  
  RESULTS
  Social isolation and loneliness were moderately correlated (r = 0.39), reflecting the separateness of these constructs, and both were associated with depression. When entered simultaneously in a regression analysis, loneliness was more robustly associated with depression. We observed similar degrees of genetic influence on social isolation (40 %) and loneliness (38 %), and a smaller genetic influence on depressive symptoms (29 %), with the remaining variance accounted for by the non-shared environment. Genetic correlations of 0.65 between isolation and loneliness and 0.63 between loneliness and depression indicated a strong role of genetic influences in the co-occurrence of these phenotypes.
  
  
  CONCLUSIONS
  Socially isolated young adults do not necessarily experience loneliness. However, those who are lonely are often depressed, partly because the same genes influence loneliness and depression. Interventions should not only aim at increasing social connections but also focus on subjective feelings of loneliness.
authors: MRC Social, Genetic and Developmental Psychiatry Centre, Institute of Psychiatry, Psychology and Neuroscience, King's College London, London, UK.
authors: Timothy
authors: T
authors: Matthews
authors: MRC Social, Genetic and Developmental Psychiatry Centre, Institute of Psychiatry, Psychology and Neuroscience, King's College London, London, UK.|Department of Child and Adolescent Psychiatry, Institute of Psychiatry, Psychology and Neuroscience, King's College London, London, UK.|National and Specialist Child Traumatic Stress and Anxiety Clinic, South London and Maudsley NHS Foundation Trust, London, UK.
authors: Andrea
authors: A
authors: Danese
authors: MRC Social, Genetic and Developmental Psychiatry Centre, Institute of Psychiatry, Psychology and Neuroscience, King's College London, London, UK.
authors: Jasmin
authors: J
authors: Wertz
authors: Sanford School of Public Policy, Duke University, Durham, NC, USA.
authors: Candice L
authors: CL
authors: Odgers
authors: MRC Social, Genetic and Developmental Psychiatry Centre, Institute of Psychiatry, Psychology and Neuroscience, King's College London, London, UK.
authors: Antony
authors: A
authors: Ambler
authors: MRC Social, Genetic and Developmental Psychiatry Centre, Institute of Psychiatry, Psychology and Neuroscience, King's College London, London, UK.|Departments of Psychology and Neuroscience, Psychiatry and Behavioral Sciences, and Institute for Genome Sciences and Policy, Duke University, Durham, NC, USA.
authors: Terrie E
authors: TE
authors: Moffitt
authors: MRC Social, Genetic and Developmental Psychiatry Centre, Institute of Psychiatry, Psychology and Neuroscience, King's College London, London, UK. louise.arseneault@kcl.ac.uk.
authors: Louise
authors: L
authors: Arseneault
mesh_terms: D003863:Depression / Q000235:genetics / Q000523:psychology*; D004739:England; D005260:Female; D059647:Gene-Environment Interaction; D005824:Genetics, Behavioral; D006801:Humans; D008132:Loneliness / Q000523:psychology*; D008137:Longitudinal Studies; D008297:Male; D012044:Regression Analysis; D012934:Social Isolation / Q000523:psychology*; D014852:Wales; D055815:Young Adult
keywords: Behavioural genetics; Depression; Loneliness; Social isolation; Young adulthood