Relationship and psychiatric morbidities in siblings of children with intellectual disability: a cross-sectional, mixed-method study.

Objectives: To assess the relationship and psychiatric morbidities in siblings of children with intellectual disability (ID) and to identify themes related to positive and negative effects on the quality of sibling relationships.

Methods: Siblings of children with ID were purposively recruited from the psychiatry department of the Vardhman Mahavir Medical College, Delhi, India. Both siblings and children with ID were assessed on the Indian adaptation of the Vineland Social Maturity Scale. Additionally, siblings were assessed using the Sibling Relationship Questionnaire-Revised (SRQ-R) and the Kiddie Schedule for Affective Disorders and Schizophrenia - Present and Lifetime Version. In-depth interviews with siblings were conducted using an interview guide to explore their responses across five domains. Data were analysed thematically.

Results: In total, 90 unaffected siblings (mean age, 12.1 years) of children with ID (mean age, 12.8 years) were included in the analysis. Of the four dimensions of the SRQ-R, the mean score was highest for warmth/closeness (2.47) and lowest for rivalry (0.73). Of the 16 individual subscales, the mean score was highest for affection (3.41), followed by nurturance of siblings (3.1), and companionship (2.89). Social quotient scores of children with ID were negatively correlated with SRQ-R scores in maternal partiality (r = -0.229, p = 0.030) and positively correlated with SRQ-R scores in companionship (r = 0.276, p = 0.009), intimacy (r = 0.270, p = 0.010), competition (r = 0.277, p = 0.008), quarrelling (r = 0.345, p = 0.001), dominance by sibling (r = 0.38, p < 0.001), and dominance of sibling (r = 0.239, p = 0.023). Only a few siblings had subthreshold conduct disorder (5.6%), oppositional defiant disorder (8.9%), and attention deficit hyperactivity disorder (12.2%). Twenty siblings participated in in-depth interviews. The main themes identified were 'impact on social life', 'impact on relationships with other siblings', 'impact on relationships with parents', 'impact on personal life', and 'positive aspects'.

Conclusion: In India, the relationship between children with ID and their unaffected siblings is mainly characterised by warmth and closeness, intimacy, prosocial behaviour, companionship, similarity, admiration, and affection. Siblings of children with ID may experience a range of internalising and externalising symptoms, although most did not reach the threshold level for diagnosis.