Mental illness and cognition in relation to age at puberty: a hypothesis

Abstract

Onset of puberty is usually considered to coincide with the last major step in brain development: the elimination of some 40% of neuronal synapses. Mean pubertal age has declined by some 4 years during the last 100 years. There is a relation between age at puberty and body build, and between body build and mental illness. The difference in body build between schizophrenia (S) and manic‐depressive psychosis (MDP) is similar to that between late and early maturers. It is suggested that S affects late‐maturing individuals and MDP very early maturers. The observed marked rise in MDP and decline in the most malignant forms of S (non‐paranoid) are in agreement with MDP and S as neurodevelopmental disorders occurring at the extremes of maturation. Maturational irregularities are most likely to occur at the extremes, and it is suggested that abbreviation of the regressive process may have led to persistent redundancy of neuronal synapses in MDP and that prolongation of the process past the optimal has yielded an inadequate synaptic density in S. The lack of cerebral abnormality in the majority of MDP and the presence of only subtle structural deficits in S, are in agreement with this. The two disorders are probably as old as mankind, and early puberty is the necessary factor for the development of MDP and late puberty is the necessary factor for that of S. There is an inverse relation between spatial ability and rate of maturation, whereas verbal ability is unaffected by maturational rate. From a previous predominance in both sexes, spatial ability (Performance IQ scores) has been reduced to below verbal ability (Verbal IQ scores) in the female sex and in early maturing males.

Prefrontal cortical dopamine from an evolutionary perspective

“…This speculation is also consistent with the evolutionary psychiatric hypotheses proposed by Burns that schizophrenia emerged as a byproduct in the evolution of human social behavior [69] , by Stevens and Price that schizophrenia is an advantageous evolutionary phenotype playing the role of splitting a group when the population becomes too large [70] , and by Saugstad that the less clear cerebral lateralization in schizophrenia is associated with late, slow maturation of the cortex [71] . On the other hand, social isolation can also be stressful, which could generate an evolutionary pressure for an adaptation strategy against isolation.…”

Public Health Implications of Altered Puberty Timing

“…[42][43][44][45][46][47][48][49][50] Questionnaire studies 51 have found no relationship between an overall "psychosis proneness" score and puberty timing, but some studies found a correlation between age at menarche and age at onset of symptoms. 42,52,53 Altered pubertal timing was not found in children who received a diagnosis of schizophrenia before age 12.…”

Changing panorama of mental illness, the role of environment – a key to prevention?

“…It is generally accepted that continuous variables: height, age at puberty (rate of maturation) are multifactorially inherited. The importance of environment in relation to adult height and pubertal age is clear when we consider the 13 cm increase in mean adult height and four years decline in pubertal age in the last 100 years, a phenotypic response to improved living conditions (high protein diet) in Western Industrialized countries (Saugstad, 1989c(Saugstad, , d, 1994a.…”