Dermatoglyphics, also referred to as epidermal ridges, are the distinct patterns and lines on the hands and fingers. These ridges appear on the hands between weeks 6 and 15 during foetal development, and remain largely unchanged after this period. Alterations in the patterns and counts of dermatoglyphics may be an indication of disruption to foetal development in the early- to mid-gestation period. A triradius occurs where three ridge systems meet at a point, and occurs four times on the palm, at the base of each of the four digits (a, b, c, and d). Dermatoglyphic indices include: fingertip patterns; finger ridge counts, which are the number of ridges between the center of the fingertip patterns and their corresponding triradius; palmar ridge counts, which are the number of ridges on the palm connecting two triradii; fluctuating asymmetries, which are the differences in ridge counts or pattern types between parallel structures on the left and right hands; and the ATD angle, which is the angle formed by lines drawn from the most remote triradius near the base of the palm, to triradii a and d, located close to the index and little fingers respectively.

What is the evidence for dermatoglyphics?

Moderate to high quality evidence found a medium-sized effect of reduced total ridge count and a-b palmar ridge count in people with schizophrenia compared to controls, with no differences in ATD angle, fingertip pattern asymmetry or ridge count asymmetry.

February 2022

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Minor physical anomalies (MPAs) are subtle anatomical deviations that have little functional or aesthetic impact. They may be traced to events occurring prenatally and may represent risk markers for underlying illness susceptibility. MPAs may be important risk indicators when an individual is already at high risk of developing psychosis, for example, having a first-degree relative with psychosis, and when multiple MPAs occur together in one individual.

What is the evidence for minor physical anomalies in people with schizophrenia?

Moderate to high quality evidence found a large increase in overall MPA scores in people with schizophrenia compared to controls without schizophrenia. There were also increased MPA scores in people with schizophrenia compared to their relatives, with no differences between relatives and controls.

Moderate quality evidence suggests MPA frequency is increased in six regions: head, eyes, ears, mouth, hands and feet. Specific MPAs include tongue with irregular smooth-rough spots, single transverse palmar crease (one crease extending across the palm of the hand), syndactyly (wholly or partially united) 2nd and 3rd toes, malformed ears, low set ears, smaller head circumference, and curved fifth finger.

Moderate to high quality found no differences between people with schizophrenia and controls in second-to-fourth digit ratio, apart from the right hand of males with schizophrenia which showed increased second-to-fourth digit ratio than controls. Second-to-fourth digit ratio is constant throughout life and is the ratio of the length of the index finger (second digit) to the length of the ring finger (fourth digit) of the same hand. Higher 2D:4D ratio is suggested to be the result of lower levels of fetal testosterone.

February 2022

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Morphometrics is the measurement of the variation in the structure or form of organisms. In the mid-1900s, William Herbert Sheldon introduced the notion that there were three components that determine the morphology of a human individual: mesomorphy (musculoskeletal robustness relative to height); endomorphy (relative fatness); and ectomorphy (relative erectness or slenderness). The study of body shapes and their prevalence in both physical and mental disorders may provide insight into the biology of, and risk for, schizophrenia.

What is the evidence for morphometrics?

High quality evidence shows people with schizophrenia are often slighter shorter in height than people without schizophrenia. Moderate to low quality evidence also finds people with schizophrenia are often be more erect and slender, and have a lower body mass compared to both people without schizophrenia and people with other mental disorders.

February 2022

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Telomeres are protective caps on the ends of chromosomes. They are linked to aging as they shorten with each cell division, and when they reach a critical length the cell stops dividing or dies. Chronic stress has been associated with reduced telomere length, resulting in the recognition of an association between adverse social and environmental influences and accelerated aging. Schizophrenia has also been associated with adverse environmental influences.

What is the evidence for telomere length in people with schizophrenia?

Moderate to high quality evidence finds a medium-sized reduction in telomere length in people with schizophrenia compared to controls.

October 2020

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