Clinical psychology has evolved from a focus on assessment and diagnosis to also include prevention and intervention methods. Early views attributed mental illness to demonic possession but thinkers like Hippocrates and Pinel emphasized natural causes and humane treatment. Formal psychological testing and assessment developed in the late 1800s and expanded during World Wars to evaluate recruits. Psychotherapy origins included Freudian psychoanalysis but behaviorism and cognitive-behavioral approaches later became prominent evidence-based interventions. Clinical psychology now emphasizes both the scientific study of psychopathology and assessment/treatment of those with emotional/behavioral problems.