Implications of co-twin dependence for twins' social interactions, mental health and alcohol use : A follow-up study of Finnish twins from adolescence to early adulthood

Objective: The aim of the present study was to examine co-twin dependence and its impact on twins' social contacts, leisure-time activities and psycho-emotional well-being. The role of co-twin dependence was also examined as a moderator of genetic and environmental influences on alcohol use in adolescence and in early adulthood. Methods: The present report is based on the Finnish Twin Cohort Study (FinnTwin16), a population-based study of five consecutive birth cohorts of Finnish twins born in the years 1975-1979. Baseline assessments were collected through mailed questionnaires, within two months of the twins' sixteenth birthday yielding replies from 5563 twin individuals. All respondent twins were sent follow-up questionnaires at ages of 17, 18½, and in early adulthood, when twins were 22-27 years old. Measures: The questionnaires included a survey of health habits and attitudes, a symptom checklist and questions about twins' relationships with parents, peers and co-twin. Measures used were twins' self-reports of their own dependence and their co-twin's dependence at age 16, reports of twins' leisure-time activities and social contacts, alcohol use, psychological distress and somatic symptoms both in adolescence and in early adulthood. Results: In the present study 25.6% of twins reported dependence on their co-twin. There were gender and zygosity differences in dependence, females and MZ twins were more likely to report dependence than males and DZ twins. Co-twin dependence can be viewed on one hand as an individual characteristic, but on the other hand as a pattern of dyadic interaction that is mutually regulated and reciprocal. Most of the twins (80.7%) were either concordantly co-twin dependent or concordantly co-twin independent. The associations of co-twin dependence with twins' social interactions and psycho-emotional characteristics were relatively consistent both in adolescence and in early adulthood. Dependence was related to higher contact frequency and a higher proportion of shared leisure-time activities between twin siblings at the baseline and the follow-up. Additionally co-twin dependence was associated with elevated levels of psycho-emotional distress and somatic complaints, especially in adolescence. In the framework of gene-environment interaction, these results suggest that the genetic contribution to individual differences in drinking patterns is dependent on the nature of the pair-wise relationship of twin siblings. Conclusions: The results of this study indicate that co-twin dependence is a genuine feature of the co-twin relationship and shows the importance of studying the impact of various features of co-twin relationships on individual twins' social and psycho-emotional life and well-being. Our study also offers evidence that differences in inter-personal relationships contribute to the effects of genetic propensities.

Early-onset depressive disorders,related mental health disorders and substance use-A prospective : longitudinal study of Finnish twins born 1983-1987

Early-onset psychiatric illnesses effects scatter to academic achievements as well as functioning in familial and social environments. From a public health point of view, depressive disorders are the most significant mental health disorders that begin in adolescence. Using prospective and longitudinal design, this study aimed to increase the understanding of early-onset depressive disorders, related mental health disorders and developing substance use in a large population-derived sample of adolescent Finnish twins. The participants of this study, FinnTwin12, an ongoing longitudinal population-based study, came from Finnish families with twins born in 1983-87 (exhaustive of five birth cohorts, identified from Finland s Central Population Register). With follow-up ongoing at age 20-24, this thesis assessed adolescent mental health in the first three waves, starting from baseline age 11-12 to follow-ups at age 14 and 17½. Some 5600 twins participated in questionnaire assessments of a wide range of health related behaviors. Mental health was further assessed among an intensively studied subsample of 1852 adolescents, who completed also professionally administered interviews at age 14, which provided data for full DSM-IV/III-R (Diagnostic and Statistical Manual for Mental Health disorders, 4th and 3rd editions) diagnoses. The participation rates of the study were 87-92%. The results of the study suggest, that the diagnostic criteria for major depressive disorder (MDD) may not capture youth with clinically significant early-onset depressive conditions outside clinical settings. Milder cases of depression, namely adolescents fulfilling the diagnostic criteria for minor depressive disorder, a qualitatively similar condition to MDD with fewer symptoms are also associated with marked suicidal thoughts, plans and attempts, recurrences and a high degree of comorbidity. Prospectively and longitudinally, early-onset depressive disorders were of substantial importance in the context of other mental health disorders and substance use behaviors: These data from a large population-derived sample established a substantial overlap between early-onset depressive disorders and attention deficit hyperactivity disorder in adolescent females, both of them significantly predictive for development of substance use among girls. Only in females baseline DSM-IV ADHD symptoms were strong predictors of alcohol abuse and dependence and illicit drug use at age 14 and frequent alcohol use and illicit drug use at age 17.½ when conduct disorder and previous substance use were controlled for. Early-onset depressive disorders were also prospectively and longitudinally associated to daily smoking behavior, smokeless tobacco use, frequent alcohol use and illicit drug use and eating disorders. Analysis of discordant twins suggested that these predictive associations were independent of familial confounds, such as family income, structure and parental models. In sum, early-onset depressive disorders predict subsequent involvement of substance use and psychiatric morbidity. A heightened risk for substance use is substantial also among those depressed below categorical diagnosis of MDD. Whether early recognition and interventions among these young people hold potential for substance use prevention further in their lives has potential public health significance and calls for more research. Data from this population-derived sample with balanced representation of boys and girls, suggested that boys and girls with ADHD behaviors may differ from each other in their vulnerability to substance use and depressive disorders: the data suggest more adverse substance use outcome for girls that was not attenuated by conduct disorder or previous substance use. Further, the prospective associations of early-onset depressive disorders and future elevated levels of addictive substance use is not explained by familial factors supporting future substance use, which could have important implications for substance use prevention.

Health-Related Quality of Life and Mental Disorders in Finland

Quality of life (QoL) and Health-related quality of life (HRQoL) are becoming one of the key outcomes of health care due to increased respect for the subjective valuations and well-being of patients and an increasing part of the ageing population living with chronic, non-fatal conditions. Preference-based HRQoL measures enable estimation of health utility, which can be useful for rational rationing, evidence-based medicine and health policy. This study aimed to compare the individual severity and public health burden of major chronic conditions in Finland, including and focusing on reliably diagnosed psychiatric conditions. The study is based on the Health 2000 survey, a representative general population survey of 8028 Finns aged 30 and over. Depressive, anxiety and alcohol use disorders were diagnosed with the Composite International Diagnostic Interview (M-CIDI). HRQoL was measured with the 15D and the EQ-5D, with 83% response rate. This study found that people with psychiatric disorders had the lowest 15D HRQoL scores at all ages, in comparison to other main groups of chronic conditions. Considering 29 individual conditions, three of the four most severe (on 15D) were psychiatric disorders; the most severe was Parkinson s disease. Of the psychiatric disorders, chronic conditions that have sometimes been considered relatively mild - dysthymia, agoraphobia, generalized anxiety disorder and social phobia - were found to be the most severe. This was explained both by the severity of the impact of these disorders on mental health domains of HRQoL, and also by the fact that decreases were widespread on most dimensions of HRQoL. Considering the public health burden of conditions, musculoskeletal disorders were associated with the largest burden, followed by psychiatric disorders. Psychiatric disorders were associated with the largest burden at younger ages. Of individual conditions, the largest burden found was for depressive disorders, followed by urinary incontinence and arthrosis of the hip and knee. The public health burden increased greatly with age, so the ageing of the Finnish population will mean that the disease burden caused by chronic conditions will increase by a quarter up to year 2040, if morbidity patterns do not change. Investigating alcohol consumption and HRQoL revealed that although abstainers had poorer HRQoL than moderate drinkers, this was mainly due to many abstainers being former drinkers and having the poorest HRQoL. Moderate drinkers did not have significantly better HRQoL than abstainers who were not former drinkers. Psychiatric disorders are associated with a large part of the non-fatal disease burden in Finland. In particular anxiety disorders appear to be more severe and have a larger public health burden than previously thought.

Living arrangements and health

In line with major demographic changes in other Northern European and North American countries and Australia, being nonmarried is becoming increasingly common in Finland, and the proportion of cohabiters and of persons living alone has grown in recent decades. Official marital status no longer reflects an individual s living arrangement, as single, divorced and widowed persons may live alone, with a partner, with children, with parents, with siblings, or with unrelated persons. Thus, more than official marital status, living arrangements may be a stronger discriminator of one s social bonds and health. The general purpose of this study was to deepen our current understanding of the magnitude, trends, and determinants of ill health by living arrangements in the Finnish working-age population. Distinct measures of different dimensions of poor health, as well as an array of associated factors, provided a comprehensive picture of health differences by living arrangements and helped to assess the role of other factors in the interpretation of these differences . Mortality analyses were based on Finnish census records at the end of 1995 linked with cause-of-death registers for 1996 2000. The data included all persons aged 30 and over. Morbidity analyses were based on two comparable cross-sectional studies conducted twenty years apart (the Mini-Finland Survey in 1978 80 and the Health 2000 Survey in 2000 01). Both surveys were based on nationally representative samples of Finns aged 30 and over, and benefited from high participation rates. With the exception of mortality analyses, this study focused on health differences among the working-age population (mortality in age groups 30-64 and 65 and over, self-rated health and mental health in the age group 30-64, and unhealthy alcohol use in the age group 30-54). Compared with all nonmarried groups, married men and women exhibited the best health in terms of mortality, self-rated health, mental health and unhealthy alcohol use. Cohabiters did not differ from married persons in terms of self-rated health or mental health, but did exhibit excess unhealthy alcohol use and high mortality, particularly from alcohol-related causes. Compared with the married, persons living alone or with someone other than a partner exhibited elevated mortality as well as excess poor mental health and unhealthy alcohol use. By all measures of health, men and women living alone tended to be in the worst position. Over the past twenty years, SRH had improved least among single men and women and widowed women, and most among cohabiting women. The association between living arrangements and health has many possible explanations. The health-related selection theory suggests that healthy people are more likely to enter and maintain a marriage or a consensual union than those who are unhealthy (direct selection) or that a variety of health-damaging behavioural and social factors increase the likelihood of ill health and the probability of remaining without a partner or becoming separated from one s partner (indirect selection). According to the social causation theory, marriage or cohabitation has a health-promoting effect, whereas living alone or with others than a partner has a detrimental effect on health. In this study, the role of other factors that are mainly assumed to reflect selection, appeared to be rather modest. Social support, which reflects social causation, contributed only modestly to differences in unhealthy alcohol use by living arrangements, but had a larger effect on differences in poor mental health. Socioeconomic factors and health-related behaviour, which reflect both selection and causation, appeared to play a more important role in the excess poor health of cohabiters and of persons living alone or with someone other than a partner, than of married persons. Living arrangements were strongly connected to various dimensions of ill health. In particular, alcohol consumption appeared to be of great importance in the association between living arrangements and health. To the extent that the proportion of nonmarried persons continues to grow and their health does not improve at the same rate as that of married persons, the challenges that currently nonmarried persons pose to public health will likely increase.

Circadian Rhythm Disruptions and Health

The doctoral thesis defined connections between circadian rhythm disruptions and health problems. Sleep debt, jet-lag, shift work, as well as transitions into and out of the daylight saving time may lead to circadian rhythm disruptions. Disturbed circadian rhythm causes sleep deprivation and decrease of mood and these effects may lead to higher accident rates and trigger mental illnesses. Circadian clock genes are involved in the regulation of the cell cycle and metabolism and thus unstable circadian rhythmicity may also lead to cancer development. In publications I-III it was explored how transitions into and out of the daylight saving time impact the sleep efficiency and the rest-activity cycles of healthy individuals. Also it was explored whether the effect of transition is different in fall as compared to spring, and whether there are subgroup specific differences in the adjustment to transitions into and out of daylight saving time. The healthy participants of studies I-III used actigraphs before and after the transitions and filled in the morningness-eveningness and seasonal pattern assessment questionnaires. In publication IV the incidence of hospital-treated accidents and manic episodes was explored two weeks before and two weeks after the transitions into and out of the daylight saving time in years 1987-2003. In publication V the relationship between circadian rhythm disruption and the prevalence of Non-Hodgkin lymphoma was studied. The study V consisted of all working aged Finns who participated in the national population census in 1970. For our study, all the cancers diagnosed during the years 1971-1995 were extracted from the Finnish Cancer Register and linked with the 1970 census files. In studies I-III it was noticed that transitions into and out of the daylight saving time disturbs the sleep-wake cycle and the sleep efficiency of the healthy participants. We also noticed that short sleepers were more sensitive than long sleepers for sudden changes in the circadian rhythm. Our results also indicated that adaptation to changes in the circadian rhythm is potentially sex, age and chronotype-specific. In study IV no significant increase in the occurrence of hospital treated accidents or manic episodes was noticed. However, interesting observations about the seasonal fluctuation of the occurrence rates of accidents and manic episodes were made. Study V revealed that there might be close relationship between circadian rhythm disruption and cancer. The prevalence of Non-Hodgkin lymphoma was the highest among night workers. The five publications included in this thesis together point out that disturbed circadian rhythms may have adverse effect on health. Disturbed circadian rhythms decrease the quality of sleep and weaken the sleep-wake cycle. A continuous circadian rhythm disruption may also predispose individuals to cancer development. Since circadian rhythm disruptions are common in modern society they might have a remarkable impact on the public health. Thus it is important to continue circadian rhythm research so that better prevention and treatment methods can be developed. Keywords: Circadian rhythm, daylight saving time, manic episodes, accidents, Non-Hodgkin lymphoma 11