Amir Levine

Attached (2010) took adult attachment theory, until then mostly an academic literature, and reduced it to three categories a reader could apply to their own dating life: anxious, avoidant and secure. Amir Levine wrote it with Rachel S. F. Heller. He is a medical doctor and associate professor of clinical psychiatry at Columbia University, working in child and adolescent psychiatry, and he runs a laboratory studying how the adolescent brain develops and why that period raises vulnerability to addiction and mood disorders. Heller holds a master's degree from Columbia and practises as a psychologist, combining attachment ideas with cognitive behavioural and acceptance and commitment therapy. The book has sold more than three million copies and been translated into dozens of languages, and a large industry of quizzes and coaching has grown around it. Worth knowing when reading it: academic attachment research usually measures anxiety and avoidance on continuous scales, so the three neat types are a simplification of the science behind them.