Sex-specific impact of early-life adversity on chronic pain: a large population-based study in Japan

Impact of Early-Life Adversity on Cannabis Use: Exploring the Mediating and Moderating Effects of Chronic Pain

Background: Although research suggests that early-life adversity (ELA) and cannabis use are linked, researchers have not established factors that mediate or modify this relationship. Identifying such factors could help in developing targeted interventions. We explored chronic pain as a potential mediator or moderator of this relationship. Methods: Using an online study, we collected cross-sectional data about ELA, cannabis use, and chronic pain to test whether ELA (adverse childhood experiences total score) is associated with cannabis use, and to examine pain as a potential mediator or moderator. Cannabis use was examined two ways: times used per day, and categorized as non-, some, or regular use. Chronic pain was measured as present/absent and as the number of painful body locations (0-8). Analyses used linear and multinomial regression. Results: ELA, chronic pain, and cannabis use were common among respondents. ELA was strongly associated with both measures of cannabis use. The number of painful body locations modestly mediated the association of ELA with cannabis use, reducing the magnitude of regression coefficients by about 1/7. The number of painful body locations modified the association between ELA and cannabis use (p≤0.006), while chronic pain presence/absence (a less-informative measure) had only a nonsignificant modification effect (p≥0.10). When either ELA or pain was high, the other was not associated with cannabis use; when either ELA or pain was low, more painful locations or higher ELA (respectively) was associated with more intense cannabis use. Conclusion: These exploratory findings suggest the importance of ELA and chronic pain as factors contributing to cannabis use, and of accounting for these factors in developing treatment and prevention strategies addressing cannabis use.

Changes in opioid receptors, opioid peptides and morphine antinociception in mice subjected to early life stress

Recent studies have shown that the endogenous opioid system is considerably affected by early life stress such as child abuse. Here, we investigated whether early life stress changes the endogenous opioid receptors and their peptides, and if such stress impacts morphine antinociception. We used mice affected by maternal separation and social isolation (MSSI) as an early life stress model. In the tail-flick test, 10-week-old MSSI mice showed a significant decrease in morphine antinociception compared to age-matched control mice. The number of c-Fos-positive cells increased in the periaqueductal gray (PAG), nucleus accumbens, and thalamus of control mice after the morphine injections, whereas hardly any positive cells were detected in the same areas of MSSI mice. The expression of μ- and κ-opioid receptor (MOR and KOR, respectively) messenger RNA (mRNA) was significantly decreased in the PAG of MSSI mice, whereas KOR expression was significantly increased in the amygdala of MSSI mice. The expression of δ-opioid receptor (DOR) mRNA was significantly reduced in the PAG and rostral ventromedial medulla of MSSI mice compared to control mice. Moreover, the lack of morphine antinociception was observed in 18-week-old MSSI mice. Our findings suggest that the supraspinal opioid system may be affected by early life stress exposure, and that this exposure may impact morphine antinociception.

Association of body mass index with chronic pain prevalence: a large population-based cross-sectional study in Japan

PURPOSE

The aim of this study was to examine the association between body mass index and chronic pain.

METHODS

The outcome was chronic pain prevalence by body mass index (BMI). BMIs of less than 18.5, 18.5-25.0, 25.0-30.0, and 30.0 or over kg/m² were defined as underweight, normal weight, overweight, and obese.

SUBJECTS

We used data from 4993 participants (2464 men and 2529 women aged 20-79 years) of the Pain Associated Cross-sectional Epidemiological survey in Japan. Sex-stratified multivariable-adjusted odds ratios were calculated with 95% confidence intervals using a logistic regression model including age, smoking, exercise, sleep time, monthly household expenditure, and presence of severe depression. We analyzed all ages and age subgroups, 20-49 and 50-79 years.

RESULTS

The prevalence of chronic pain was higher among underweight, overweight, and obese male respondents than those reporting normal weight, with multivariable odds ratios of 1.52 (1.03-2.25), 1.55 (1.26-1.91), and 1.71 (1.12-2.60). According to underweight, only older men showed higher prevalence of chronic pain than normal weight men with odd ratios, 2.19 (1.14-4.20). Being overweight and obese were also associated with chronic pain in women; multivariable odds ratios were 1.48 (1.14-1.93) and 2.09 (1.20-3.64). Being underweight was not associated with chronic pain.

CONCLUSION

There was a U-shaped association between BMI and chronic pain prevalence among men ≥ 50 years, and a dose-response association among women. Our finding suggests that underweight should be considered in older men suffering chronic pain.