Christian Hakulinen

University of Helsinki | HY · Department of Psychology

Background The associations of social isolation and loneliness with premature mortality are well known, but the risk factors linking them remain unclear. We sought to identify risk factors that might explain the increased mortality in socially isolated and lonely individuals. Methods We used prospective follow-up data from the UK Biobank cohort st...

Personality is suggested to be a major risk factor for depression but large-scale individual participant meta-analyses on this topic are lacking. Data from 10 prospective community cohort studies with 117,899 participants (mean age 49.0 years; 54.7% women) were pooled for individual participant meta-analysis to determine the association between per...

Background: Higher depressive symptoms have been associated with lower future income. However, studies examining this issue have had limited follow-up times and have used self-reported measures of income. Also, possible confounders or mediators have not been accounted. Methods: 971 women and 738 men were selected from the ongoing prospective You...

To investigate cross-sectional and longitudinal associations between personality and smoking, and test whether sociodemographic factors modify these associations. Cross-sectional and longitudinal individual-participant meta-analysis. Nine cohort studies from Australia, Germany, UK and US. A total of 79,757 men and women (mean age = 51 years). Perso...

The role of personality as a determinant of alcohol consumption has long been debated, but prospective evidence is scarce. We performed individual participant meta-analysis to examine the association between the Five-Factor Model personality traits (extraversion, neuroticism, agreeableness, conscientiousness, and openness to experience) and alcohol...

Objectives Healthcare registers are invaluable resources for research. Partly overlapping register entries and preliminary diagnoses may introduce bias. We compare various methods to address this issue and provide fully reproducible open‐source R scripts. Methods We used all Finnish healthcare registers 1969–2020, including inpatient, outpatient a...

Background: Intergenerational transmission of mental disorders has been well established, but it is unclear whether exposure to a child's mental disorder increases parents' subsequent risk of mental disorders. We examined the association of mental disorders in children with their parents' subsequent mental disorders. Methods: In this population bas...

Importance Previous research indicates that mental disorders may be transmitted from one individual to another within social networks. However, there is a lack of population-based epidemiologic evidence that pertains to the full range of mental disorders. Objective To examine whether having classmates with a mental disorder diagnosis in the ninth...

Background: Fertility rates have declined during the 2010s in many high-income countries, with a strong decrease in Finland. Mental disorders might contribute to this decline, given that they became a major cause of work disability in Finland. We examined associations between broad and specific categories of mental disorders and the likelihood of h...

Evidence on the intergenerational continuity of loneliness and on potential mechanisms that connect loneliness across successive generations is limited. We examined the association between loneliness of (G0) parents (859 mothers and 570 fathers, mean age 74 years) and their children (G1) (433 sons and 558 daughters, mean age 47 years) producing 991...

Life satisfaction and purpose in life are fundamental yet separate ways to evaluate one’s life. Both positively predict physical health and longevity, making them key factors for length and quality of life. However, we do not know which of them predicts mortality, when controlling for the influence of each other. Given that purpose in life involves...

Importance Although incidence of suicide in depression varies remarkably temporally, risk factors have been modeled as constant and remain uncharted in the short term. How effectively factors measured at one point in time predict risk at different time points is unknown. Objective To examine the absolute risk and risk factors for suicide in hospit...

Objectives: Healthcare registers are invaluable resources for research. Partly overlapping register entries and preliminary diagnoses may introduce bias. We compare various methods to address this issue and provide fully reproducible open-source R scripts. Methods: We used all Finnish healthcare registers 1969-2020, including inpatient, outpatient...

Children from low-income households have more mental disorders, although these connections have rarely been studied in terms of mental health service utilization in population-based data. In this national register-based cohort study all persons born and living in Finland with their families from 1991 to 2017 (n = 1 520 415) were followed until firs...

Aims Although seasonality has been documented for mental disorders, it is unknown whether similar patterns can be observed in employee sickness absence from work due to a wide range of mental disorders with different severity level, and to what extent the rate of change in light exposure plays a role. To address these limitations, we used daily bas...

This study aims to evaluate the directionality of the association between loneliness and cognitive performance in older adults, accounting for confounding factors. Data were from 55,662 adults aged ≥50 years who participated in Waves 5–8 of the Survey of Health, Ageing and Retirement in Europe (SHARE). Loneliness was assessed with the Three-Item Lo...

Background In previous studies, null results from sibling comparison designs have been used to infer that no causal association exists between childhood family income and subsequent risk of mental disorders. The aim of our study is to replicate the findings from previous studies and propose three alternative explanations based on i) variability in...

Purpose In Finland, prevalence of schizophrenia is higher in the eastern and northern regions and co-occurs with the distribution of schizophrenia polygenic risk scores. Both genetic and environmental factors have been hypothesized to contribute to this variation. We aimed to examine the prevalence of psychotic and other mental disorders by region...

School grades in adolescence have been linked to later psychiatric outcomes, but large-scale nationwide studies across the spectrum of mental disorders are scarce. In the present study, we examined the risk of a wide array of mental disorders in adulthood, as well as the risk of comorbidity, associated with school achievement in adolescence. We use...

Background In Finland, prevalence of schizophrenia is higher in the eastern and northern regions and co-occurs with the distribution of schizophrenia polygenic risk scores. Both genetic and environmental factors have been hypothesized to contribute to this variation, but its reasons are not fully understood. We aimed to examine the prevalence of ps...

Background A study was undertaken to examine the association between multiple indicators of socioeconomic position (SEP) at the age of 30 and the subsequent risk of the most common mental disorders. Methods All persons born in Finland between 1966 and 1986 who were alive and living in Finland at the end of the year when they turned 30 were include...

Background Although loneliness and social isolation have been linked to an increased risk of non-communicable diseases such as cardiovascular disease and dementia, their association with the risk of severe infection is uncertain. We aimed to examine the associations between loneliness and social isolation and the risk of hospital-treated infections...

While sunlight may influence cognitive function through several pathways, associations of residential sunlight exposure with cognitive function are not well known. We evaluated associations of long-term residential sunlight exposure with cognitive function among a representative cohort of 1838 Finnish adults residing in Finland who underwent compre...

Background Mental disorders can affect workforce participation via a range of mechanisms. In this study, we aimed to estimate the association between different types of mental disorders and working years lost, defined as the number of years not actively working or enrolled in an educational programme. Methods In this population-based cohort study,...

Background Season of birth is a risk factor of schizophrenia, and it is possible that cumulative exposure to climatic factors during childhood affects the risk of schizophrenia. We conducted a cohort study among 365,482 persons born in Finland in 1990–1995 to examine associations of 10-year cumulative exposure to global solar radiation and ambient...

Background Depression may be associated with lower likelihood of having children, but the findings are inconsistent. Previous population-based studies on the topic are limited. Objectives We examined associations between depression and the likelihood of having children, the number of children, and the age at first birth; and whether these associat...

Substantial genetic correlations have been reported across psychiatric disorders and numerous cross-disorder genetic variants have been detected. To identify the genetic variants underlying general psychopathology in childhood, we performed a genome-wide association study using a total psychiatric problem score. We analyzed 6,844,199 common SNPs in...

(1) Background: For decades, the temperaments of infants and small children have been a focus of studies in human development and been seen as a potential contributor to children’s developmental patterns. However, less is known about the interplay between the temperamental characteristics of mothers and their children in the context of explaining v...

While characteristics of psychosocial work environment have traditionally been studied separately, we propose an alternative approach that treats psychosocial factors as interacting elements in networks where they all potentially affect each other. In this network analysis, we used data from a prospective occupational cohort including 10,892 partic...

Evidence suggests that sunlight counteracts depression, but the associations of long-term sunlight exposure with specific symptoms of depression are not well known. We evaluated symptom-specific associations of average 1-year solar insolation with DSM-5 depressive symptoms in a representative cohort of Finnish adults. The sample included 1,845 part...

Employment is rare among people with a schizophrenia diagnosis. Meanwhile, a genetic liability for schizophrenia may hinder labour market performance. We studied how the polygenic risk score (PGS) for schizophrenia related to education and labour market outcomes. We found that a higher PGS was linked to lower educational levels and weaker labour ma...

Objective To investigate the genetic architecture of internalizing symptoms in childhood and adolescence. Method In 22 cohorts, multiple univariate genome-wide association studies (GWASs) were performed using repeated assessments of internalizing symptoms, in a total of 64,561 children aged between 3 and 18. Results were aggregated in meta-analyse...

Background Social isolation and loneliness have been associated with increased risk of dementia, but it is not known whether this risk is modified or confounded by genetic risk of dementia. Methods We used the prospective UK Biobank study with 155 070 participants (mean age 64.1 years), including self-reported social isolation and loneliness. Gene...

Aim Parents’ psychological problems may affect children’s screen time, but research has been scarce. We examined the association between parental psychological problems and children’s screen media behaviours in a nationally representative sample. Methods The participants were from the Adolescent Brain Cognitive Development study, recruited by prob...

Background Infections have been hypothesised to increase the risk of dementia. Existing studies have included a narrow range of infectious diseases, relied on short follow-up periods, and provided little evidence for whether the increased risk is limited to specific dementia subtypes or attributable to specific microbes rather than infection burden...

We analysed (A) the association of short‐term as well as long‐term cumulative exposure to natural light, and (B) the association of detailed temporal patterns of natural light exposure history with three indicators of sleep: sleep duration, sleep problems, and diurnal preference. Data (N = 1,962; 55% women; mean age 41.4 years) were from the prospe...

Background/aim: To examine the association between sense of coherence (SOC) and health-related quality of life (HRQoL) in early breast cancer patients. Patients and methods: The study population included 406 disease-free breast cancer survivors who participated in 3-year and 5-year follow-ups of a randomized exercise intervention. SOC was assess...

We test whether genetic influences that explain individual differences in aggression in early life also explain individual differences across the life-course. In two cohorts from The Netherlands ( N = 13,471) and Australia ( N = 5628), polygenic scores (PGSs) were computed based on a genome-wide meta-analysis of childhood/adolescence aggression. In...

According to the network theory strong associations between symptoms drive the disease process. We compared those with and without diagnosed depressive disorders (DD+/DD-) and analysed the effects of differences in (a) network connectivity, (b) symptom thresholds, and (c) autoregressive loops (i.e. how strongly specific symptoms predict themselves)...

Background The secular decline in labor market participation and the concurrent increase in opioid use in many developed countries have sparked a policy debate on the possible connection between these two trends. We examined whether the use of prescription opioids was connected to labor market outcomes relating to participation, employment and unem...

Childhood aggressive behavior (AGG) has a substantial heritability of around 50%. Here we present a genome-wide association meta-analysis (GWAMA) of childhood AGG, in which all phenotype measures across childhood ages from multiple assessors were included. We analyzed phenotype assessments for a total of 328 935 observations from 87 485 children ag...

DNA methylation profiles of aggressive behavior may capture lifetime cumulative effects of genetic, stochastic, and environmental influences associated with aggression. Here, we report the first large meta-analysis of epigenome-wide association studies (EWAS) of aggressive behavior ( N = 15,324 participants). In peripheral blood samples of 14,434 p...

Lack of social contacts has been associated with an increased risk of cancer mortality, but it is not known whether living alone increases the risk of cancer incidence or case fatality. We examined the association between living alone with cancer incidence, case-fatality and all-cause mortality in eight most common cancers. All patients with their...

Objective The suggestion from cross-review comparison that lower levels of social integration (social isolation, loneliness) and cigarette smoking are equally powerful predictors of premature mortality has been promulgated by policy organisations and widely reported in the media. For the first time, we examined this assertion by simultaneously comp...

Background We examined, (a) whether in early childhood exposure to risky family environment in different domains (socioeconomic, mental, parenting practices, health behavior, and child-related risks) and accumulatively across various domains (cumulative risk) is associated with child's problem behavior at age 9, and (b) whether the association is m...

Importance Combining information on polygenic risk scores (PRSs) with other known risk factors could potentially improve the identification of risk of depression in the general population. However, to our knowledge, no study has estimated the association of PRS with the absolute risk of depression, and few have examined combinations of the PRS and...

Background Links between parental socioeconomic position during childhood and subsequent risks of developing mental disorders have rarely been examined across the diagnostic spectrum. We conducted a comprehensive analysis of parental income level, including income mobility, during childhood and risks for developing mental disorders diagnosed in sec...

Objectives To examine employment and earnings trajectories before and after the first sickness absence period due to major depressive disorder (MDD). Methods All individuals (n=158 813) in Finland who had a first sickness absence period (lasting longer than 9 days) due to MDD between 2005 and 2015 were matched with one randomly selected individual...

PurposePutative causal relations among depressive symptoms in forms of network structures have been of recent interest, with prior studies suggesting that high connectivity of the symptom network may drive the disease process. We examined in detail the network structure of depressive symptoms among participants with and without depressive disorders...

Internalising symptoms in childhood and adolescence are as heritable as adult depression and anxiety, yet little is known of their molecular basis. This genome-wide association meta-analysis of internalising symptoms included repeated observations from 64,641 individuals, aged between 3 and 18. The N-weighted meta-analysis of overall internalising...

DNA methylation profiles of aggressive behavior may capture lifetime cumulative effects of genetic, stochastic, and environmental influences associated with aggression. Here, we report the first large meta-analysis of epigenome-wide association studies (EWAS) of aggressive behavior (N=15,324 participants). In peripheral blood samples of 14,434 part...

Purpose A prominent labour market feature in recent decades has been the increase in abstract and service jobs, while the demand for routine work has declined. This article examines whether the components of Type A behaviour predict workers' selection into non-routine abstract, non-routine service and routine jobs. Design/methodology/approach Buil...

Substantial genetic correlations have been reported across psychiatric disorders and numerous cross-disorder genetic variants have been detected. To identify the genetic variants underlying general psychopathology in childhood, we performed a genome-wide association study using a total psychiatric problem score. We analyzed 6,844,199 common SNPs in...

The short versions of the General Health Questionnaire (GHQ-12), Beck's Depression Inventory (BDI-6), and Mental Health Index (MHI-5) are all valid and reliable measures of general psychological distress, depressive symptoms, and anxiety. We tested the psychometric properties of the scales, their overlap, and their ability to predict mental health...

Background: Infectious diseases have been hypothesised to increase the risk of dementia. However, the evidence is sparse, captures only a limited range of infectious diseases, and relies on short follow-up periods. We assessed a wide range of severe (hospital-treated) bacterial and viral infections and their subtypes as risk factors for dementia in...

Background and aims: Previous studies have shown that prescription opioid use is more common in the socioeconomically disadvantaged communities in the US. This study examined the area and individual-level determinants of prescription opioid use in Finland during the period 1995-2016. Design: Logistic regression analysis using nationwide data on...

Background and objectives Temperament may be associated with eating behaviors over the lifespan. This study examined the association of toddlerhood temperament with dietary behavior and dietary intervention outcomes across 18 years. Methods The study comprised 660 children (52% boys) from The Special Turku Intervention Project (STRIP), which is a...

The association between socioeconomic disadvantage and increased risk of depressive symptoms in adulthood is well established. We tested A the contribution of early exposure to neighborhood socioeconomic disadvantage on later depressive symptoms throughout life, B the persistence of the potential association of early exposure with depressive sympto...

Objective: To examine the associations of social isolation and loneliness with incident dementia by level of genetic risk. Design: Prospective population-based cohort study. Setting and participants: 155 074 men and women (mean age 64.1, SD 2.9 years) from the UK Biobank Study, recruited between 2006 and 2010. Main exposures: Self-reported social i...

Importance The association between income and mental health has long been a question of interest. Nationwide register data provide means to examine trends and patterns of these associations. Objectives To compare income-specific trends in the incidence rates of first psychiatric hospital admissions and to evaluate whether an income gradient exists...

Background Human aggressive behavior (AGG) has a substantial genetic component. Here we present a large genome-wide association meta-analysis (GWAMA) of childhood AGG. Methods We analyzed assessments of AGG for a total of 328,935 observations from 87,485 children (aged 1.5 – 18 years), from multiple assessors, instruments, and ages, while accounti...

Objective: Individuals with severe mental disorders have an impaired ability to work and are likely to receive income transfer payments as their main source of income. However, the magnitude of this phenomenon remains unclear. Using longitudinal population cohort register data, the authors conducted a case-control study to examine the levels of em...

Purpose Individuals with schizophrenia have been reported to have low employment rates. We examined the associations of schizophrenia with employment, income, and status of cohabitation from a work life course perspective. Methods Nationwide cohort study including all individuals (n = 2,390,127) born in Denmark between 1955 and 1991, who were aliv...

Background Mood disorders have been associated with poor socioeconomic outcomes, but there is a lack of large-scale population-based studies on the topic. We examined associations between bipolar disorder and depression with an onset between ages 15 and 25, and subsequent socio-economic outcomes (employment, income and educational attainment) using...

Importance Evidence linking parental socioeconomic position and offspring’s schizophrenia risk has been inconsistent, and how risk is associated with parental socioeconomic mobility has not been investigated. Objective To elucidate the association between parental income level and income mobility during childhood and subsequent schizophrenia risk....

Background: Mood disorders are known to be associated with poor socioeconomic outcomes, but no study has examined these associations across the entire worklife course. Our goal was to estimate the associations between bipolar disorder and depression in early adulthood and subsequent employment, income, and educational attainment. Methods: We con...

Objective: We examined how personality traits of the Five Factor Model were related to years of healthy life years lost (mortality and disability) for individuals and the population. Method: Participants were 131,195 individuals from 10 cohort studies from Australia, Germany, the United Kingdom, and the United States (n=43,935 from 7 cohort stud...

Objective: To examine the associations between an onset of serious mental disorders before the age of 25 with subsequent employment, income, and education outcomes. Methods: Nationwide cohort study including individuals (n=2 055 720) living in Finland between 1963 and 1990, who were alive at the end of the year they turned 25. Mental disorder di...

Objective: To determine the association between cumulative exposure to parent-reported childhood adversities and self-reported adulthood suboptimal sleep. Methods: Participants (n = 1,038; 57.4% women) were drawn from the prospective population-based Young Finns Study. Childhood adversities were assessed in 1980 among 3- to- 18-year-olds, while...

Research shows that people select themselves and are selected into occupations, partly because of their personality, and this has implications for their person-environment fit. Although it has been shown that personality congruence between the individual and the environment is important to job satisfaction, the effect of personality congruence in o...

Intergenerational transmission of life satisfaction has been empirically established, but less is known about the continuity of satisfaction as being reflected across multiple life domains, unique effects of parental domain-specific satisfaction on offspring overall life satisfaction, and potential gender effects. In this population-based prospecti...

Background Genomic analysis of the child might offer new potential to illuminate human parenting. We examined whether offspring (G2) genome‐wide genotype variation (SNPs) is associated with their mother's (G1) emotional warmth and intolerance, indicating a gene–environment correlation. If this association is stronger than between G2′s genes and the...

Personality traits are related to health behaviours, but it is unknown whether changes in personality would lead to changes in health behaviours. We examined whether naturally occurring, within‐individual variation in personality traits over time is associated with corresponding changes in smoking, physical activity, alcohol consumption, and body m...

International adoptees are at an increased risk of emotional and behavioral problems, especially those who are adopted at an older age. We took a new approach in our study of the network structure and predictability of emotional and behavioral problems in internationally adopted children in Finland. Our sample was from the on-going adoption study a...

The oxytocin receptor gene (OXTR) may function as a “plasticity gene” that increases or decreases sociability in those individuals susceptible to growing up in a beneficial versus more adverse environment. This study used data from 2289 (55% female) participants from the ongoing prospective Young Finns Study. Maternal emotional warmth was assessed...

Background: Lack of social support is an established risk factor across health outcomes, making it important to examine its family environmental and genetic determinants. Methods: In a 27-year follow-up of the Young Finns Study (N=2341), we examined with a latent growth curve model whether genes involved in the oxytocin signaling pathway—namely, o...

Objective To examine whether social isolation and loneliness (1) predict acute myocardial infarction (AMI) and stroke among those with no history of AMI or stroke, (2) are related to mortality risk among those with a history of AMI or stroke, and (3) the extent to which these associations are explained by known risk factors or pre-existing chronic...

Background: Personality influences an individual's adaptation to a specific job or organization. Little is known about personality trait differences between medical career and specialty choices after graduating from medical school when actually practicing different medical specialties. Moreover, whether personality traits contribute to important c...

Background Personality has been associated with alcohol use, but less is known about how alcohol use may influence long-term personality trait change. Methods The present study examines associations between alcohol use and change in the five major personality traits across two measurement occasions (mean follow-up of 5.6 years). A total of 39 722...

We examined whether physicians' personality traits moderate the association between medical specialty and well-being at work. Nationally representative sample of Finnish physicians (n = 2,815; 65% women; aged 25 to 72 years in 2015) was used. Personality was assessed with the shortened Big Five Inventory. Indicators of well-being at work were measu...

We modeled early psychosocial risks as a network of interconnected variables to study their associations with later depressive symptoms and cardiometabolic outcomes. The participants were a nationally representative sample of 2580 men and women aged 3-18 years in 1980. Their parents reported the psychosocial risks in 1980, including the following:...

Objective: The aim of this study was to examine (a) whether adventurous and explosive temperament profiles (presumed precursors of antisocial and borderline personality) are associated with character traits over a 15-year follow-up and (b) whether social support and attachment security modify the relationship between temperament profiles and chara...

The aim of this study was to examine (a) the associations of temperament and character dimensions with paranoid ideation over a 15-year follow-up in the general population (b) the associations of explosive temperament and organized character profiles with paranoid ideation. 2137 subjects of the Young Finns Study completed the Temperament and Charac...

Background: The aim of this study was to examine longitudinally in the general population (a) whether depressive symptoms co-occur with paranoid ideation from late adolescence to middle age (b) whether depressive subsymptoms are differently linked with paranoid ideation (c) whether depressive symptoms are associated with state-level or trait-level...

Background: Social relations are important for health, particularly at older ages. We examined the salience of frequency of social contacts and marital status for cognitive ageing trajectories over 21 years, from midlife to early old age. Methods: Data are from the Whitehall II cohort study, including 4290 men and 1776 women aged 35-55 years at...

It has been suggested that biological markers are associated with human happiness. We contribute to the empirical literature by examining the independent association between various aspects of biometric wellbeing measured in childhood and happiness in adulthood. Using Young Finns Study data (n = 1905) and nationally representative linked data we ex...

Using the Young Finns Study (YFS) combined with the Finnish Linked Employer-Employee Data (FLEED) we show that quantities of creatine measured in 1980 prior to labour market entry affect labour market outcomes over the period 1990-2010. Those with higher levels of creatine (proxied by urine creatinine) prior to labour market entry spend more time i...

Sleep problems are common and impair the health and productivity of employees. Work characteristics constitute one possible cause of sleep problems, and sleeping poorly might influence wellbeing and performance at work. This study examines the reciprocal associations between sleep problems and psychosocial work characteristics. The participants wer...

Introduction: Type 2 diabetes is a public health concern, but psychosocial factors that may protect against the disease are unknown. This study examines whether a positive psychosocial environment in childhood is associated with lower risk for Type 2 diabetes in adulthood or healthier glucose trajectories over the life course, and whether BMI medi...