Effect of Parental–Child Age Gaps and Skipped-Generation Families on Comorbidities Related to Attention Deficit Hyperactivity Disorder: A Population-Based Case–Control Study

<b>Background</b>: While attention deficit/hyperactivity disorder (ADHD) is characterized by neurodevelopmental heterogeneity, the influence of familial structural factors-particularly parental age and skipped-generation caregiving-on comorbidity patterns remains insufficiently studied. This study examined the associations between parent-child age gaps, skipped-generation family structures, and psychiatric comorbidities in children with ADHD. <b>Methods</b>: Data came from Taiwan's NHIRD (2009-2013), including 79,163 ADHD cases and 395,815 matched controls. Key variables included maternal and paternal age at childbirth and grandparent-paid insurance premiums as a proxy for skipped-generation caregiving. Conditional logistic regression was used to estimate odds ratios (ORs) for 20 psychiatric and developmental comorbidities. <b>Results</b>: Children with ADHD exhibited significantly higher odds of various comorbidities, including oppositional defiant disorder (OR = 147.05, 95% CI = 101.0-214.1), somatoform disorder (OR = 25.78, 95% CI = 7.96-83.46), anxiety disorder (OR = 24.49, 95% CI = 17.9-33.5), emotional disturbances during childhood and adolescence (OR = 13.99, 95% CI = 9.15-21.4), and autism spectrum disorder (OR = 8.07, 95% CI = 6.63-9.82). Advanced maternal age (>35 years) was associated with increased odds of autism spectrum disorder (OR = 1.47, 95% CI: 1.29-1.67) and speech/language delay (OR = 1.33, 95% CI: 1.17-1.52), whereas younger maternal age (≤25 years) was linked to higher odds of anxiety disorder (OR = 1.23, 95% CI: 1.13-1.33) and adjustment reaction (OR = 1.41, 95% CI: 0.95-2.11). Maternal age under 20 years showed the highest odds for bipolar disorder (OR = 2.01, 95% CI: 1.04-3.88). For paternal age, older age (>35 years) was associated with increased odds of autism (OR = 1.14, 95% CI: 1.04-1.26) and speech/language delay (OR = 1.15, 95% CI: 1.04-1.27), whereas paternal age ≤20 years was strongly linked to bipolar disorder (OR = 3.58, 95% CI: 1.54-8.32) and anxiety (OR = 1.39, 95% CI: 1.01-1.93). Children from skipped-generation families-defined as grandparent-paid insurance premiums without parental cohabitation-had significantly higher odds of bipolar disorder (OR = 2.88, 95% CI: 1.36-6.11), personality disorder (OR = 9.23, 95% CI: 2.23-38.20), adjustment reaction (OR = 2.23, 95% CI: 1.39-3.59), and emotional disturbances during childhood/adolescence (OR = 1.69, 95% CI: 1.13-2.54). <b>Conclusions</b>: Both extremes of parental age and skipped-generation caregiving are linked to specific associations with certain psychiatric comorbidity patterns in children with ADHD. These findings highlight the importance of integrating family structure into diagnostic assessments and treatment planning and support the development of targeted early interventions.