The influence of gender, age, Psychological resilience and family interaction factors upon generalised anxiety disorder (GAD) and major depressive disorder (MDD) was investigated in 75 non-autism spectrum disorder (NASD) siblings who had a brother or sister with an autism spectrum disorder (ASD). GAD and MDD were much more prevalent than in comparable age group samples, and adolescent females had the highest MDD rates. Several Psychological resilience skills were significantly associated with lower GAD and MDD, particularly being able to recognise mistakes in their thinking (for children) and being able to remain in control of their anger (for adolescents). Suggestions are made for ways of encouraging NASD siblings to develop skills that may assist them in avoiding these disorders.