Short-term exposure to temperature and mental health in North Carolina: a distributed lag nonlinear analysis

Abstract

Adverse mental health outcomes have been associated with high temperatures in studies worldwide. Few studies explore a broad range of mental health outcomes, and to our knowledge, none are specific to NC, USA. This ecological study explored the relationship between ambient temperature and mental health outcomes (suicide, self-harm and suicide ideation, anxiety and stress, mood disorders, and depression) in six urban counties across the state of NC, USA. We applied a quasi-Poisson generalized linear model combined with a distributed lag nonlinear model (DLNM) to examine the short-term effects of daily ambient temperature on emergency admissions for mental health conditions (2016 to 2018) and violent deaths (2004 to 2018). The results were predominately insignificant, with some key exceptions. The county with the greatest temperature range (Wake) displays higher levels of significance, while counties with the lowest temperature ranges (New Hanover and Pitt) are almost entirely insignificant. Self-harm and suicidal ideation peak in the warm months (July) and generally exhibit a protective effect at lower temperatures and shorter lag intervals. Whereas anxiety, depression, and major depressive disorders peak in the cooler months (May and September). Suicide is the only outcome that favored a 20-day lag period in the sensitivity analysis, although the association with temperature was insignificant. Our findings suggest additional research is needed across a suite of mental health outcomes to fully understand the effects of temperatures on mental health.

Keywords: Ambient temperature; Anxiety; Depression; Distributed lag nonlinear model; Mental health; Self-harm; Suicide.

Fig. 1

Map of NC counties included in the study area

Fig. 2

The distributed lag effects of average temperature readings on the relative risk (RR) of emergency department visits for anxiety disorders, major depressive disorders, mood disorders, and self-harm and ideation relative to the median average temperatures in Buncombe County, NC (2016–2018). Dashed lines represent the 1st, 25th, 50th, 75th, and 99th temperature quantiles, respectively

Fig. 3

The distributed lag effects of average temperature readings on the relative risk of emergency department visits for anxiety disorders, major depressive disorders, mood disorders, and self-harm and ideation relative to the median average temperatures in Mecklenburg County, NC (2016–2018). Dashed lines represent the 1st, 25th, 50th, 75th, and 99th temperature quantiles, respectively

Fig. 4

The three-dimensional plot summarizes the temperature, lag, and relative risk relationship of emergency department visits for anxiety disorders, major depressive disorders, mood disorders, and self-harm and ideation in Mecklenburg County, NC (2016–2018)

Fig. 5

The distributed lag effects of average temperature readings on the relative risk of emergency department visits for anxiety disorders, major depressive disorders, mood disorders, and self-harm and ideation relative to the median average temperatures in Wake County, NC (2016–2018). Dashed lines represent the 1st, 25th, 50th, 75th, and 99th temperature quantiles, respectively

Fig. 6

The distributed lag effects of average temperature readings on the relative risk of emergency department visits for anxiety disorders, major depressive disorders, mood disorders, and self-harm and ideation relative to the median average temperatures in New Hanover County, NC (2016–2018). Dashed lines represent the 1st, 25th, 50th, 75th, and 99th temperature quantiles, respectively

Fig. 7

The distributed lag effects of average temperature readings on the relative risk of emergency department visits for anxiety disorders, major depressive disorders, mood disorders, and self-harm and ideation relative to the median average temperatures in Pitt County, NC (2016–2018). Dashed lines represent the 1st, 25th, 50th, 75th, and 99th temperature quantiles, respectively

Fig. 8

The distributed lag effects of average temperature readings on the relative risk of emergency department visits for anxiety disorders, major depressive disorders, mood disorders, and self-harm and ideation relative to the median average temperatures in Buncombe County, NC (2016–2018). Dashed lines represent the 1st, 25th, 50th, 75th, and 99th temperature quantiles, respectively

Fig. 9

The distributed lag effects of average temperature readings on the relative risk of suicide relative to the median average temperatures in Mecklenburg, Buncombe, Guilford, and Wake counties (2016–2018). Dashed lines represent the 1st, 25th, 50th, 75th, and 99th temperature quantiles, respectively