Examining the relationship of concurrent obesity and tobacco use disorder on the development of substance use disorders and psychiatric conditions: Findings from the NESARC-III.

Background: Multimorbidity is linked to worse health outcomes than single health conditions. However, recent studies show that obesity may reduce the risk of developing substance use disorders (SUDs), particularly in vulnerable populations. We investigated how comorbid obesity and tobacco use disorder (TUD) relate to the risk of SUDs and psychiatric conditions. Methods: Data was used from 36,309 individuals who completed the National Epidemiological Survey on Alcohol and Related Conditions - Wave III. Individuals who met the DSM-5 criteria for TUD in the last year were defined as the TUD group. Obesity was defined as having a body mass index (BMI) greater than 30 kg/m2. Using this information, individuals were grouped into categories, with people being identified as either having obesity, TUD, both obesity and TUD, or not having either obesity or TUD (comparison). Groups were compared against their comorbid diagnoses of either an additional SUD or psychiatric conditions. Results: Controlling for demographic characteristics, we found that individuals with obesity including those individuals with TUD, had lower rates of comorbid SUD diagnosis than individuals with TUD alone. Additionally, individuals with combined TUD and obesity, and those with TUD alone, had the highest rates of comorbid psychiatric disorder diagnosis. Conclusions: The current study aligns with previous research suggesting that obesity may reduce risk of substance use disorders, even in individuals who have other risk factors promoting harmful substance use (e.g., tobacco use). These findings may inform targeted intervention strategies for this clinically relevant subpopulation.

Technical note: Application of the Box-Cox data transformation to animal science experiments.

In the use of ANOVA for hypothesis testing in animal science experiments, the assumption of homogeneity of errors often is violated because of scale effects and the nature of the measurements. We demonstrate a method for transforming data so that the assumptions of ANOVA are met (or violated to a lesser degree) and apply it in analysis of data from a physiology experiment. Our study examined whether melatonin implantation would affect progesterone secretion in cycling pony mares. Overall treatment variances were greater in the melatonin-treated group, and several common transformation procedures failed. Application of the Box-Cox transformation algorithm reduced the heterogeneity of error and permitted the assumption of equal variance to be met.

Effects of melatonin implants in pony mares. 2. Long-term effects.

The effects of melatonin implant treatment over a 4 wk period at the summer solstice on the transition into and out of the following anovulatory season were evaluated in ovary-intact and ovariectomized mares. Melatonin implants tended to delay the timing of the final ovulation of the breeding season (P = 0.0797) in the ovary-intact mares. Although the decline in LH secretion associated with the end of the breeding season was parallel between treatments and ovarian statuses, the rate of LH secretion, as expressed by its mathematical accumulation, was lower in ovariectomized, melatonin-treated mares than in ovariectomized, control mares suggesting that melatonin administration advanced the offset of the breeding season in ovariectomized mares (P = 0.0001). The first ovulation of the subsequent breeding season was significantly delayed in the melatonin-treated mares as compared with that of control mares (P = 0.0031). During reproductive recrudescence, the time of the onset of the increase in LH secretion was similar among all 4 groups but the patterns of LH secretion were different for each treatment and ovarian status combination (P = 0.0112). Mares with melatonin implants had a slower rate of increase in LH secretion than control mares (P = 0.0001), and ovariectomized mares had a faster rate of LH increase than intact mares (P = 0.0001). These results suggest that melatonin implants during the summer solstice can alter the annual reproductive rhythm in mares and support the concept that endocrine patterns of reproductive recrudescence are not entirely independent of the ovary.

Effects of melatonin implants in pony mares. 1. Acute effects.

The effects of melatonin implant treatment over a four week period on LH, estradiol (E2) and progesterone (P4) secretion during the breeding season were studied in ovary-intact and ovariectomized pony mares. Mares with melatonin implants had significantly higher daytime melatonin concentrations than mares with sharm implants (P = 0.0065). In ovariectomized mares, LH secretion did not differ between mares with melatonin and sham implants. In ovary-intact mares, melatonin implants altered the pattern of LH secretion (P = 0.0023) in such a way that an increase in LH secretion was observed during the periovulatory period. Estradiol and P4 secretion were unaffected by melatonin implants. These results suggest that constant administration of melatonin may enhance the secretion of LH during the periovulatory surge but does not adversely affect E2, P4 or basal LH secretion in mares during the breeding season.