As life expectancy increases globally, psychotherapy for people aged 65 years and above must become more specialized and competent. In this Review, Laidlaw et al. describe findings from gerontological and psychological research that seek to improve mental health interventions in late life and enhance older adults’ emotional capabilities and motivations.

Despite widespread adoption of diversity initiatives grounded in psychological insights, evidence for their effectiveness is mixed. In this Review, He et al. present behavioural design as a promising avenue for bridging individual-level and system-level approaches to organizational diversity.

Adolescents are particularly at risk for social contagion effects of self-harm. In this Review, Chen et al. specify factors that exacerbate self-harm social contagion at the individual, interpersonal, community and societal levels and discuss how to bridge psychological and public health perspectives to mitigate self-harm risk in this age group.

Machine learning algorithms can increase the effectiveness of mental health interventions, but biased systems might exacerbate current disparities in case identification and treatment. In this Perspective, Timmons et al. propose a model that integrates artificial intelligence methods with co-creation techniques to reduce bias and increase inclusion in mental healthcare.