BackgroundBeing born with low birth weight may have an impact on different aspects of mental health, psychosocial functioning and well-being; however results from studies in young adulthood have so far yielded mixed findings. The aim of this study was to assess the long-term impact in young adulthood on self-reported mental health, health-related quality of life, self-esteem and social relations by investigating differences between two low birth weight groups and a control group.MethodsIn a follow-up at 20 years of age, 43 preterm VLBW (birth weight ≤ 1500 g), 55 term SGA (birth weight < 10th percentile) and 74 control subjects completed the Adult Self-Report (ASR) of the Achenbach System of Empirically Based Assessment, the Adult Autism Spectrum Quotient (AQ), the Short Form 36 Health Survey, the Self-Perception Profile for Adolescents-Revised, and the Wechsler Adult Intelligent Scale III assessment.ResultsThe VLBW and SGA groups reported significantly more mental health problems than controls. The VLBW group predominantly had internalizing problems, and the non-significant association with ASR Total score was reduced by the Intelligence Quotient (IQ). The SGA group had increased scores on both internalizing and externalizing problems, and the association with ASR Total score remained significant after adjusting for IQ in this group. Both low birth weight groups reported less interaction with friends and lower quality of life related to mental health domains than controls. Self-esteem scores were lower than in the control group for athletic competence (VLBW) and social acceptance (SGA).ConclusionOur findings suggest that self-reported mental health and well-being in young adulthood may be adversely affected by low birth weight, irrespective of whether this is the result of premature birth or being born SGA at term.