# Family History and Solar Insolation in Bipolar I Disorder

## TL;DR

This study found that people with bipolar I disorder living near the poles are more likely to have a family history of mood disorders, and this link is stronger for females.

## Contribution

The study reveals a novel geographical and gender-based link between solar insolation and family history of mood disorders in bipolar I patients.

## Key findings

- A family history of mood disorders is more common in bipolar I patients near the poles.
- Females with bipolar I disorder are more likely to have a family history of mood disorders.
- Solar insolation patterns correlate with the likelihood of a family history of mood disorders.

## Abstract

Sunlight has profound impacts on physical and mental health, beyond vision, including effects on circadian rhythms, alertness, mood, and sleep. A family history of any mood disorders is strongly associated with psychiatric disorders including bipolar disorder. The purpose of this study was to evaluate the association between a family history of any mood disorder in patients with bipolar I disorder and solar insolation at varied international onset locations.

Data for this analysis were available from 5842 patients with a diagnosis of bipolar I disorder obtained at 83 collection sites in both hemispheres. This included 4752 patients from 71 collection sites in the northern hemisphere and 1090 patients from 12 collection sites in the southern hemisphere. Patient data variables were obtained from records or interviews. Solar insolation data were obtained from The National Aeronautics and Space Administration (NASA) Power database for each onset location, and the ratio of the mean monthly minimum/mean monthly maximum solar insolation was calculated. Typically, the ratio is largest near the equator (little yearly change in solar insolation) and smallest near the poles (large yearly change in solar insolation).

A significant relationship was found between a family history of any mood disorder, the ratio of the mean monthly minimum/mean monthly maximum solar insolation, and gender. The odds of a family history of mood disorder increased as patient location nears the poles and decreased near the equator. Female gender also increased the odds of having a family history of a mood disorder.

This study highlighted the association between family history, solar insolation, and gender in international patients with bipolar I disorder. Given the profound effects of sunlight on human health, the family of patients with bipolar disorder who live in the same location with the same solar insolation, and especially females, may be at increased risk for a mood disorder.

Significant outcomes
○There is a significant association between family history of a mood disorder, solar insolation, and gender in international patients with bipolar I disorder.○The odds of a family history of a mood disorder increase as patient location nears the poles and decrease near the equator.○Family members who live in the same location and experience the same solar insolation, especially females, may be at increased risk for a mood disorder.
Limitations
○Family history was obtained from patient data. Family members were not interviewed.○Unique patient light exposure data was not obtained.○Individual patient sensitivity to light was not analyzed.

Significant outcomes
○There is a significant association between family history of a mood disorder, solar insolation, and gender in international patients with bipolar I disorder.○The odds of a family history of a mood disorder increase as patient location nears the poles and decrease near the equator.○Family members who live in the same location and experience the same solar insolation, especially females, may be at increased risk for a mood disorder.

There is a significant association between family history of a mood disorder, solar insolation, and gender in international patients with bipolar I disorder.

The odds of a family history of a mood disorder increase as patient location nears the poles and decrease near the equator.

Family members who live in the same location and experience the same solar insolation, especially females, may be at increased risk for a mood disorder.

Limitations
○Family history was obtained from patient data. Family members were not interviewed.○Unique patient light exposure data was not obtained.○Individual patient sensitivity to light was not analyzed.

Family history was obtained from patient data. Family members were not interviewed.

Unique patient light exposure data was not obtained.

Individual patient sensitivity to light was not analyzed.