Developmental psychopathology focuses on the interplay of personal and environmental factors in the origin of mental disorders. This includes genotype-environment interactions and epigenetic encoding of life events (e.g. prenatal stress; abuse). Computational psychiatry uses mathematical models of cognitive and neural processes (e.g. decision making) to identify the mechanisms involved in mental disorders.

Evolutionary psychopathology focuses on biological models and concepts to understand the functions of the neural and psychological processes involved in mental disorders and how they have been shaped by selection during evolutionary history. It does not necessarily consider mental disorders as dysfunctions (e.g. it may reflect an adaptive process).

The two reasons for the evolution of vulnerability are trade-offs between competing traits or functions (1) and biological conflict of interest between individuals (2). Psychopathological conditions may arise from dysfunctional mechanisms or from functional mechanisms that produce maladaptive outcomes because the present environment is different from the one in which the mechanism was developed. It is also possible that psychopathological conditions may arise due to biologically adaptive but undesired behavioural strategies.

Traits associated with autism are associated with long-term sexual relationships and traits associated with psychosis are associated with short-term sexual relationships with multiple partners. This may indicate that there is a trade-off between the two and that they lie on the same continuum. A mood disorder may arise through a trade-off between pursuing rewards and avoiding punishment (e.g. depression).

Differential susceptibility states that individuals can be more or less sensitive to the effects of experience due to a combination of genetic and early developmental factors (i.e. people more susceptible to adverse conditions are also more responsive to safe, supportive conditions). This may have arisen because individual differences in plasticity may be an adaptive response to unpredictable fluctuations in the environment. It is possible that early adversity may not impair development but adaptively shape it.

The problems of the DSM are comorbidity between disorders (1) and heterogeneity within disorders (2). Externalising disorders refer to anti-social and rule-breaking behaviour. Internalizing disorders refer to anxiety, fear and distress. Life history theory refers to the way organisms allocate time and energy to the activities that comprise their life cycle. Life history strategies are suites of morphological, physiological and behavioural traits that implement life history allocations at the individual and species level. Life-history related traits covary along a fast-slow continuum (e.g. unpredictable environments are associated with early maturation and reproduction and vice versa). The fast-slow distinction can demonstrate that some mental disorders are adaptive responses to maladaptive environments.