To Örebro University

BACKGROUND: While compromised stress resilience constitutes a recognised risk factor for somatic and psychiatric disease development in general, the knowledge about how individual variation in vulnerability to stress may specifically influence the long-term risks of disadvantageous health behaviours is limited.

METHODS: In this Swedish cohort study, we aimed to investigate the association between stress resilience in late adolescence and adult use of addictive substances. We included 9381 men with information on psychological stress resilience measured during military conscription examinations, who later responded to an extensive health survey (mean age 34.0±7.2 years) including detailed information on substance use. We modelled continuous outcomes using linear regression, binary outcomes with logistic regression and other categorical outcomes with multinomial logistic regression.

RESULTS: We found that low stress resilience in adolescence conferred increased risks of all studied measures of addictive behaviour. After adjusting for childhood socioeconomic information, low stress resilience was associated with adult current regular smoking (relative risk ratio: 5.85, 95% CI 4.32 to 7.93), higher nicotine dependence scores (beta: 0.76, 95% CI 0.29 to 1.23), hazardous use of alcohol (>14 alcoholic drink-equivalents per week, OR: 1.72, 95% CI 1.37 to 2.16), DSM-IV criteria for alcohol dependence (OR: 1.74, 95% CI 1.35 to 2.25), and drug use (OR: 1.77, 95% CI 1.51 to 2.08). The results remained largely unchanged after further adjustments for adult educational attainment and occupation as well as for additional conscription covariates.

CONCLUSION: Low stress resilience in late adolescence appears to be associated with an increased risk of disadvantageous and addictive health behaviours in adulthood.

PURPOSE: Although childhood traumatic experiences are recognized as important determinants for adolescent psychiatric health in general, our objective was to explore the specific influence of childhood bereavement on the stress resilience development trajectory.

METHODS: In this national register-based cohort study, we identified 407,639 men born in Sweden between 1973 and 1983, who underwent compulsory military enlistment examinations in late adolescence, including measures of psychological stress resilience. We defined exposure as loss of a first-degree family member in childhood, and estimated relative risk ratios (RRRs) for reduced (moderate or low), compared with high, stress resilience with 95% confidence intervals (CIs) using multinomial logistic regression.

RESULTS: Loss of a parent or sibling in childhood conferred a 49% increased risk of subsequent low stress resilience (RRR, 1.49, 95% CI, 1.41-1.57) and an 8% increased risk of moderate stress resilience (RRR, 1.08, 95% CI, 1.03-1.13) in late adolescence. There was also a graded increase in risk with increasing age at loss; teenagers were at higher risk for low resilience (RRR, 1.64, 95% CI, 1.52-1.77) than children aged 7-12 (RRR, 1.47, 95% CI, 1.34-1.61) and ≤6 years (RRR, 1.16 95% CI, 1.02-1.32). The excess risk was observed for all causes of death, including suicide and unexpected deaths as well as deaths due to other illnesses. The associations remained after exclusion of parents with a history of hospitalization for psychiatric diagnoses.

CONCLUSIONS: The long-term consequences of childhood bereavement may include lower stress resilience in late adolescence.

Accumulating evidence suggests that psychosocial stress and susceptibility to stressful exposures – stress resilience – influence the risk of various health outcomes, but the potential link with cancer occurrence is unclear. The aims of this thesis were to test if loss of a close relative, a marker of severe psychological stress, and stress resilience measured during late adolescence are associated with cancer risk later in life, as well as to explore potential underlying mechanisms. National registers provided information on childhood bereavement, defined as death of a first-degree relative, as well as a measure of psychological functioning relevant to stress resilience that was obtained from mandatory military enlistment assessments. In a cohort comprising all individuals born in Sweden during 1961-2002, we found that bereavement during childhood (up to age 18 years) was associated with increased risks of HPVrelated malignancies and pancreatic cancer. Parental loss during early adulthood (ages 18-40 years) also entails a raised risk of pancreatic cancer as well as for gastric and lung cancer. In a cohort of men born during 1973-1983, we observed that childhood bereavement is also associated with low stress resilience during late adolescence. In our third cohort study, comprising men born during 1952-1956, we found that low stress resilience compared with high, was associated with 5-fold and 3-fold increased risks of subsequent liver and lung cancer, respectively. In contrast, low stress resilience is associated with reduced risks for prostate cancer and malignant melanoma. Finally, in a cohort of twin conscripts born during 1959-1985 who completed a survey in 2005- 2006 covering use of addictive substances, we found that low stress resilience was also associated with a raised occurrence of hazardous use of alcohol, alcohol dependence, cigarette smoking and nicotine dependence, as well as with other drug use. We conclude that the observed links with cancer risk for stressful exposures and low stress resilience, may be explained, at least in part, by disadvantageous health behavior.

Background: A parental cancer diagnosis is a stressful life event, potentially leading to increased risks of mental and physical problems among children. This study aimed to investigate the associations of parental cancer with IQ, stress resilience, and physical fitness of the affected men during early adulthood.

Materials and methods: In this Swedish population-based study, we included 465,249 men born during 1973-1983 who underwent the military conscription examination around the age of 18 years. We identified cancer diagnoses among the parents of these men from the Cancer Register. IQ, stress resilience, and physical fitness of the men were assessed at the time of conscription and categorized into three levels: low, moderate, and high (reference category). We used multinomial logistic regression to assess the studied associations. Results: Overall, parental cancer was associated with higher risks of low stress resilience (relative risk ratio [RRR]: 1.09 [95% confidence interval (CI) 1.04-1.15]) and low physical fitness (RRR: 1.12 [95% CI 1.05-1.19]). Stronger associations were observed for parental cancer with a poor expected prognosis (low stress resilience: RRR: 1.59 [95% CI 1.31-1.94]; low physical fitness: RRR: 1.45 [95% CI 1.14-1.85]) and for parental death after cancer diagnosis (low stress resilience: RRR: 1.29 [95% CI 1.16-1.43]; low physical fitness: RRR: 1.40 [95% CI 1.23-1.59]). Although there was no overall association between parental cancer and IQ, parental death after cancer diagnosis was associated with a higher risk of low IQ (RRR: 1.11 [95% CI 1.01-1.24]).

Conclusion: Parental cancer, particularly severe and fatal type, is associated with higher risks of low stress resilience and low physical fitness among men during early adulthood. Men who experienced parental death after cancer diagnosis also have a higher risk of low IQ.

Background: Stress resilience is recognised as a determinant of both psychiatric and somatic health, but the potential link between stress resilience and cancer development has not been explored.

Methods: In this nationwide cohort study, we examined the association between stress resilience in adolescence and subsequent cancer risk. We identified a cohort of 284 257 Swedish men, born 1952-1956, who underwent compulsory military enlistment examinations including measures of psychological stress resilience (median age 18 years). The resulting score was categorised as low, moderate and high stress resilience. Individuals diagnosed with cancer during the follow-up time were identified through data linkage to the Swedish Cancer Register.

Results: Lowest stress resilience, compared with the highest, was associated with increased risks of liver (HR: 4.73, 95% CI 2.73 to 8.19) and lung (HR: 2.75, 95% CI 2.02 to 3.74) cancer after adjusting for markers of socioeconomic circumstances in childhood (p for trend <0.001 for both cancer types). Further adjustment for cognitive and physical fitness at conscription assessment had a marginal influence. In contrast, men with low stress resilience had a decreased risk of being diagnosed with prostate cancer (HR: 0.65, 95% CI 0.56 to 0.76) and malignant melanoma (HR: 0.65, 95% CI 0.55 to 0.76).

Conclusion: We conclude that adolescent stress resilience, plausibly by influencing behavioural choices and social patterns, constitutes an important determinant of adult cancer occurrence. Increased awareness of longterm consequences in susceptible individuals may help direct future efforts to reduce cancer burden in adults.

Background: While early-life exposure to stress has been associated with subsequent psychiatric and cardiovascular morbidity, little is known regarding its potential role in cancer development. We hypothesized that severe emotional stress, such as the loss of a parent through death during childhood, may increase the risk of cancer in early life.

Method: Based on the Swedish Multi-Generation Register, we identified a cohort of 4,219,691 individuals who had both parents identifiable in the same register and followed the cohort from birth to the age of 40 years between 1961 and 2006. Through information retrieved from the Swedish Causes of Death and Cancer Registers, we ascertained death among the parents and cancer diagnosis among the cohort individuals. We used Poisson regression to calculate the relative risks (RRs) and 95 % confidence intervals (CIs).

Results: Parental death was not associated with total cancer risk. However, parental death during childhood was associated with a higher risk of human papillomavirus (HPV) infection-related cancers (RR 1.4; 95 % CI 1.2-1.7), and loss during early adulthood (>18 years) entailed a higher risk of cancers of the stomach (RR 1.8; 95 % CI 1.3-2.6), lung (RR 1.7; 95 % CI 1.1-2.4), rectum (RR 1.4; 95 % CI 1.0-2.0), and breast (RR 1.1; 95 % CI 1.0-1.3). A significant association was observed for pancreatic cancer for both loss during childhood (RR 2.6; 95 % CI 1.6-4.2) and afterward (RR 2.8; 95 % CI 1.9-4.3).

Conclusion: Our results suggest that severe psychological stress in early life may be associated with premature development of certain malignancies, particularly cancers related to smoking and HPV infection.