Indoor tanning early in life is associated with increased risk of anxiety and depression later in life

Evidence on the temporal association of indoor tanning with depression and anxiety has been sparse. We evaluated whether indoor tanning behavior early in life is associated with risk of incident depression and anxiety later in life in the Nurses’ Health Study II (NHSII), a large well-characterized cohort of US women.¹

Early-life indoor tanning frequency was calculated based on indoor tanning usage during high school/college and between the ages of 25 and 35. Antidepressant use and clinician-diagnosed depression were measured biennially since 1997 and 2001, respectively. We used multivariable(MV)-adjusted Cox proportional hazards models to estimate hazard ratios (HRs) and 95% confidence intervals (CIs) for the association between indoor tanning frequency and risk of incident depression (defined as first occurrence of clinician-diagnosed depression and/or antidepressant use since 2001).² Anxiety was assessed through the Crown-Crisp Index (CCI)³ on the 1993 and 2005 cohort questionnaires and the Generalized Anxiety Disorder 7-item Scale (GAD-7)⁴ on the 2013 questionnaire. Anxiety-free women (CCI <6 in 1993 and 2005) who later reported having anxiety (GAD-7>=10 in 2013) were considered as incident cases. We fitted logistic regression models to estimate odds ratios (ORs) and 95% CIs for indoor tanning frequency and risk of incident anxiety. Detailed descriptions of the study population and measurement of covariates are provided in Supplementary Materials.

Compared to women who never tanned, those who used indoor tanning 1–2, 3–11, and 12+ times per year had 18%, 31%, and 46% increased risk for incident depression, respectively (Table 1). Risk of incident anxiety was also significantly increased among women who tanned indoor 3–11 times (OR=1.25, 95% 0=1.05–1.48) or 12+ times (OR=1.40, 95% 0=1.06–1.85) per year, compared to never users (Table 2). We also observed a significant linear trend of increasing risk of incident depression and anxiety across indoor tanning frequency categories (MV-adjusted p-trend<0.05).

Table 1.

HRs and 95% CIs for the association between indoor tanning frequency during early life and incident depression in the NHSII (2001–2017)

		Indoor tanning frequency				P for trend
		Never	1–2 times per year	3–11 times per year	12 + times per year
Depression definition 1 a	# of cases	8,563	1,791	1,063	275
	Person-years	393,836	69,663	33,155	8,303
	Age-adjusted HR (95% CI)	1 (ref)	1.20 (1.14–1.26)	1.49 (1.39–1.59)	1.55 (1.38–1.76)	<.0001
	MV-adjusted HR (95% CI) c	1 (ref)	1.16 (1.10–1.22)	1.41 (1.32–1.51)	1.40 (1.24–1.59)	<.0001
Depression definition 2 b	# of cases	4,372	951	527	152
	Person-years	425,191	76,062	36,843	9,168
	Age-adjusted HR (95% CI)	1 (ref)	1.22 (1.13–1.31)	1.38 (1.26–1.51)	1.62 (1.37–1.91)	<.0001
	MV-adjusted HR (95% CI) c	1 (ref)	1.18 (1.09–1.26)	1.31 (1.20–1.44)	1.46 (1.24–1.72)	<.0001

^aDepression defined as clinician-diagnosed depression or anti-depressive medication use.

^bDepression defined as clinician-diagnosed depression and anti-depressive medication use.

^cCox model adjusted for age (in months, continuous), major ancestry (white, non-white), BMI (<22, 22–23, 24–25, 26–27, 28–29, 30 or more, kg/m²), pack year of smoking (1–9, 10–19, 20–29, 30 or more, pack-years), alcohol intake (0, 0.1–4.9, 5–14.9, 15–29.9, 30 or more, g/day), caffeine intake (quintiles), calories per day (quintiles), physical activity (quartiles), hair color (black, brown, blonde, red), number of moles on both legs (0, 1–5, 6–14, 15 or more), number of blistering sunburns between ages 15–20 (0, 1–4, 5–9, 10 or more), pain score (continuous), average hours of sleep per day (<5, 5, 6, 7, 8, 9, 10 or more), difficulty falling asleep (rarely or never, sometimes, most of the time), night shift work (no night shift work, 0–2 yrs, 3–5 yrs, 6–9 yrs, 10–14 yrs, 15–19 yrs, 20 or more yrs), age at menopause (54 or older, 50–53, 45–49, 20–44), hormone replacement therapy use (premenopause, postmenopause-never use hormone, postmenopause- current use of hormones, postmenopause-past use of hormones), history of cardiovascular disease (yes/no), history of diabetes (yes/no), history of hypertension (yes/no), ambient erythemal ultraviolet radiation (in quintiles), alternative healthy eating index-2010 (in quintiles), self-perceived body shape at age 20 (diagram 1–2, 3–4, 5–9, Supplementary Figure 1), and highest degree obtained by current spouse (high school or below, college, graduate).

NOTE: For BMI, pack year of smoking, alcohol intake, caffeine intake, calories per day, physical activity, ambient erythemal ultraviolet radiation, and alternative healthy eating index-2010, cumulative average prior to each follow-up cycle were calculated and controlled in the Cox model.

Table 2.

ORs and 95% CIs for the association between indoor tanning during early life and incident anxiety in the NHSII

	Indoor tanning frequency				P for trend
	Never	1–2 times per year	3–11 times per year	12+ times per year
# of cases	1,244	271	176	61
Total # of participants	37,181	6,874	3,476	974
Age-adjusted OR (95% CI)	1 (ref)	1.11 (0.97–1.27)	1.40 (1.19–1.65)	1.71 (1.31–2.24)	<.0001
MV-adjusted OR (95% CI) a	1 (ref)	1.06 (0.92–1.21)	1.25 (1.05–1.48)	1.40 (1.06–1.85)	0.0013

^aLogistic regression analysis adjusting for age, major ancestry (white, nonwhite), BMI (<22, 22–23, 24–25, 26–27, 28–29, 30 or more, kg/m²), pack year of smoking (1–9, 10–19, 20–29, 30 or more, pack-years), alcohol intake (0, 0.1–4.9, 5–14.9, 15–29.9, 30 or more, g/day), caffeine intake (quintiles), calories per day (quintiles), physical activity (quartiles), hair color (black, brown, blonde, red), number of moles on both legs (0, 1–5, 6–14, 15 or more), number of blistering sunburns between ages 15–20 (0, 1–4, 5–9, 10 or more), pain score (continuous variable), average hours of sleep per day (<5, 5, 6, 7, 8, 9, 10 or more), difficulty falling asleep (rarely or never, sometimes, most of the time), night shift work (no night shift work, 0–2 yrs, 3–5 yrs, 6–9 yrs, 10–14 yrs, 15–19 yrs, 20 or more yrs), age at menopause (54 or older, 50–53, 45–49, 20–44), hormone replacement therapy use (premenopause, postmenopause-never use hormone, postmenopause- current use of hormones, postmenopause-past use of hormones), history of cardiovascular disease (yes/no), diabetes history (yes/no), history of hypertension (yes/no), ambient erythemal ultraviolet radiation (in quintiles), alternative healthy eating index-2010 (in quintiles), self-perceived body shape at age 20 (diagram 1–2, 3–4, 5–9, Supplementary Figure 1), and highest degree obtained by current spouse (high school or below, college, graduate).

Here, despite excluding individuals with history of depression and anxiety and adjusting for a comprehensive set of confounding factors, we observed positive association between early-life indoor tanning frequency and risk of depression and anxiety later in life. The present study provides evidence that tanning behavior may precede clinical indicators of depression and anxiety. Ultraviolet radiation from indoor tanning induces the production of beta-endorphin, an endogenous opioid that can relieve pain and improve mood.⁵ Our data showed frequent indoor tanners were more likely to report pain, long-term night shift works, and difficulty falling asleep, suggesting tanning was possibly used for self-medicating. Individuals who used indoor tanning more frequently also consumed more cigarettes, alcohol, and caffeine. Additionally, 13% of women who tanned 12+ times per year viewed themselves as having higher than average body somatotype while eating roughly the same calories per day as non-tanners, indicating image consciousness and possible subclinical or clinical body dysmorphia. (Supplementary Table 1) These findings suggest that frequent indoor tanning is an early behavioral sign of individuals who are prone to depression and anxiety and it tends to co-occur with other addictive behaviors. Clinicians should be aware of these associations and may recommend psychiatric interventions for highly frequent users of indoor tanning.