Tom Rosenström

Pairwise Measures of Causal Direction in the Epidemiology of Sleep Problems and Depression

Depressive mood is often preceded by sleep problems, suggesting that they increase the risk of depression. Sleep problems can also reflect prodromal symptom of depression, thus temporal precedence alone is insufficient to confirm causality. The authors applied recently introduced statistical causal-discovery algorithms that can estimate causality from cross-sectional samples in order to infer the direction of causality between the two sets of symptoms from a novel perspective. Two common-population samples were used; one from the Young Finns study (690 men and 997 women, average age 37.7 years, range 30–45), and another from the Wisconsin Longitudinal study (3101 men and 3539 women, average age 53.1 years, range 52–55). These included three depression questionnaires (two in Young Finns data) and two sleep problem questionnaires. Three different causality estimates were constructed for each data set, tested in a benchmark data with a (practically) known causality, and tested for assumption violations using simulated data. Causality algorithms performed well in the benchmark data and simulations, and a prediction was drawn for future empirical studies to confirm: for minor depression/dysphoria, sleep problems cause significantly more dysphoria than dysphoria causes sleep problems. The situation may change as depression becomes more severe, or more severe levels of symptoms are evaluated; also, artefacts due to severe depression being less well presented in the population data than minor depression may intervene the estimation for depression scales that emphasize severe symptoms. The findings are consistent with other emerging epidemiological and biological evidence.

Temperament and character traits predict future burden of depression

BACKGROUND Personality traits are associated with depressive symptoms and psychiatric disorders. Evidence for their value in predicting accumulation of future dysphoric episodes or clinical depression in long-term follow-up is limited, however. METHODS Within a 15-year longitudinal study of a general-population cohort (N=751), depressive symptoms were measured at four time points using Beck׳s Depression Inventory. In addition, 93 primary care patients with DSM-IV depressive disorders and 151 with bipolar disorder, diagnosed with SCID-I/P interviews, were followed for five and 1.5 years with life-chart methodology, respectively. Generalized linear regression models were used to predict future number of dysphoric episodes and total duration of major depressive episodes. Baseline personality was measured by the Temperament and Character Inventory (TCI). RESULTS In the general-population sample, one s.d. lower Self-directedness predicted 7.6-fold number of future dysphoric episodes; for comparison, one s.d. higher baseline depressive symptoms increased the episode rate 4.5-fold. High Harm-avoidance and low Cooperativeness also implied elevated dysphoria rates. Generally, personality traits were poor predictors of depression for specific time points, and in clinical populations. Low Persistence predicted 7.5% of the variance in the future accumulated depression in bipolar patients, however. LIMITATIONS Degree of recall bias in life charts, limitations of statistical power in the clinical samples, and 21-79% sample attrition (corrective imputations were performed). CONCLUSION TCI predicts future burden of dysphoric episodes in the general population, but is a weak predictor of depression outcome in heterogeneous clinical samples. Measures of personality appear more useful in detecting risk for depression than in clinical prediction.

Body-image dissatisfaction is strongly associated with chronic dysphoria.

BACKGROUND Individual depressive symptoms may contribute to the risk of chronic depression. This study aimed to explore which symptoms predict chronic dysphoria, a hallmark of depression. METHODS 1057 participants from the population-based Young Finns study were examined for four times during a 16-year period. Those with a modified Becks Depression Inventory score in the upper third at all four screenings were considered to have chronic dysphoria (n=135). Participants with only one high depression score formed the reference group of transient dysphoria (n=179). Individual items of the Inventory were analyzed in terms of their association with dysphoria status and chronicity, controlling for potential confounding factors, such as personality assessed using the Temperament and Character Inventory. RESULTS Body-image dissatisfaction was strongly associated with chronically elevated dysphoria (Bonferroni-corrected p=0.006). The degree of body-image dissatisfaction was associated with the probability for chronic dysphoria in a dose-response manner, with the estimated probability ranging from 0.01 to 0.60 as a function of item response. The association remained after adjustments for a wide range of personality characteristics. LIMITATIONS The study relied on self-reports of mood and personality, and lacked information on external opinion on participants appearances. The requirement of full time-series data may have resulted in attrition-related bias. CONCLUSIONS Body-image dissatisfaction was a strong predictor of chronic depression characterized by dysphoria. This finding suggests that dysfunctional attitude towards oneself might represent a potentially important target for cognitive therapies and preventive interventions.

Associations between dimensional personality measures and preclinical atherosclerosis: The cardiovascular risk in Young Finns study

OBJECTIVE To assess how multidimensional personality-trait theories, such as the Psychobiological Model of Temperament and Character, and the Five-factor Model of Personality, are associated with subclinical atherosclerosis as indicated by carotid intima-media thickness (IMT). The analysis was designed to tolerate non-linear development in which the same personality profiles can have multiple final outcomes and different antecedent profiles can have the same final outcome. METHODS 605 men and 844 women (average age 31.6year, s.d.=5.0, range=24-39) provided data on IMT and traits of the psychobiological model, 725 men and 1011 women were assessed for IMT and the five-factor model (age 37.7year, s.d.=5.0, range=30-45). Robust multidimensional Hotellings T(2) statistic was used to detect personality differences between participants with high IMT and others. Model-based clustering method further explored the effect. RESULTS Those with a high level of subclinical atherosclerosis within the sample (highest IMT-decile) had a combined higher persistence (i.e., were perseverative or perfectionistic), more disorganized (schizotypal) character, and more antisocial temperamental configuration than others (P=0.019). No effect was found for the five-factor model (P=0.978). Traditional methods that did not account for multidimensionality and nonlinearity did not detect an association. CONCLUSION Psychological well-being may have positive effects on health that reduce atherosclerosis in the population as a whole. Increased subclinical atherosclerosis was associated with a profile that combines known risk factors, such as cynical distrust and hostile tendencies. More frequent use of statistical procedures that can cope with non-linear interactions in complex psychobiological systems may facilitate scientific advances in health promotion.

Temperament and depressive symptoms: What is the direction of the association?

BACKGROUND Temperament characteristics have been suggested to be associated with mental health outcomes, especially depression, but the direction of the association is unknown. In this study, we tested whether temperament characteristics, as defined by the Buss-Plomin adulthood emotionality-activity-sociability (EAS) temperament model, predict depressive symptoms or whether depressive symptoms predict changes in temperament characteristics. METHODS Participants comprised a population-based sample of 719 men and 1020 women from the Young Finns study aged 20-35 years at baseline in 1997 and who responded to repeated surveys of temperament and depressive symptoms in four study phases from 1997 to 2012. The associations were tested using linear regression models, repeated cross-lagged structural equation models, parallel latent growth curve models and two-dimensional continuous-time state space model (Exact Discrete Model). RESULTS Both low sociability (β=-0.12, p<0.001) and high negative emotionality (β=0.34, p<0.001) predicted subsequent increased depressive symptoms, whereas earlier depressive symptoms predicted increased negative emotionality (β=0.50, p<0.001), but not low sociability. LIMITATIONS The depressive symptoms scale applied may not be used for measuring clinically recognized depression. CONCLUSIONS Our findings suggest that the direction of the association is from low sociability to depressive symptoms rather than the reverse, but the association between negative emotionality and depressive symptoms seems to be reciprocal.

Exploring Causality between TV Viewing and Weight Change in Young and Middle-Aged Adults. The Cardiovascular Risk in Young Finns Study

Background Television viewing time (TV time) is associated with increased weight and obesity, but it is unclear whether this relation is causal. Methods and Results We evaluated changes in TV time, waist circumference (waist) and body mass index (BMI) in participants of the population-based Cardiovascular Risk in Young Finns study (761 women, 626 men aged 33–50 years in 2011). Waist and BMI were measured, and TV time was self-reported in 2001, 2007, and 2011. Changes in waist and BMI between 2001 and 2011 were studied a) for the whole group, b) in groups with constantly low (≤1 h/d), moderate (1–3 h/d), or high (≥3 h/d) TV time, and c) in groups with ≥1 hour in-/decrease in daily TV time between 2001 and 2011. BMIs in 1986 were also evaluated. We explored the causal relationship of TV time with waist and BMI by classical temporality criterion and recently introduced causal-discovery algorithms (pairwise causality measures). Both methods supported the hypothesis that TV time is causative to weight gain, and no evidence was found for reverse or bidirectional causality. Constantly low TV time was associated with less pronounced increase in waist and BMI, and waist and BMI increase was lower with decreased TV time (P<0.05). The increase in waist and BMI was at least 2-fold in the high TV time group compared to the low TV time group (P<0.05). Adjustment for age, sex, BMI/waist in 2001, physical activity, energy intake, or smoking did not change the results. Conclusions In young and middle-aged adults, constantly high TV time is temporally antecedent to BMI and waist increase.

Temperament and character predict body-mass index: a population-based prospective cohort study.

OBJECTIVE Personality is a potential factor determining individual differences in body-weight change. The current study examines associations between personality traits and change in body-mass index (BMI) over six years. METHOD The participants were 762 women and 648 men aged 24-39 years at the base-line. Personality was assessed with the Temperament and Character Inventory (TCI). For calculating BMI, height and weight were assessed at a clinic. RESULTS Longitudinal analyses conducted with linear regressions showed that in men and women, higher Novelty seeking predicted higher BMI (p<.05), whereas lower Reward dependence predicted higher BMI in women (p<.05) when baseline BMI was taken into account. In addition, cross-sectional associations for several TCI traits were found in age and education adjusted analyses. In women, higher Self transcendence (p<.05) was associated with higher BMI. In men, higher Novelty seeking (p<.001) and Self transcendence (p<.01) and lower Self directedness (p<.01) and Cooperativeness (p<.05) were associated with higher BMI. In addition, analyses of variance were conducted for multidimensional trait profiles (trait combinations). Significant temperament profile related differences in BMI were found in all analyses in women. Associations with character profiles and in men were less consistent. CONCLUSION The results give support for personality playing a role in weight gain. Knowledge on personality may be used for motivating weight loss and designing weight management interventions.

Temperament, character and suicide attempts in unipolar and bipolar mood disorders

OBJECTIVE Personality features may indicate risk for both mood disorders and suicidal acts. How dimensions of temperament and character predispose to suicide attempts remains unclear. METHOD Patients (n = 597) from 3 prospective cohort studies (Vantaa Depression Study [VDS], Jorvi Bipolar Study [JoBS], and Vantaa Primary Care Depression Study [PC-VDS]) were interviewed at baseline, at 18 months, and, in VDS and PC-VDS, at 5 years (1997-2003). Personality was measured with the Temperament and Character Inventory-Revised (TCI-R), and follow-up time spent in major depressive episodes (MDEs) as well as lifetime (total) and prospectively ascertained suicide attempts during the follow-up were documented. RESULTS Overall, 219 patients had 718 lifetime suicide attempts; 88 patients had 242 suicide attempts during the prospective follow-up. The numbers of both the total and prospective suicide attempts were associated with low self-directedness (β = -0.266, P = .004, and β = -0.294, P < .001, respectively) and high self-transcendence (β = 0.287, P = .002, and β = 0.233, P = .002, respectively). Total suicide attempts were linked to high novelty seeking (β = 0.195, P = .05). Prospective, but not total, suicide attempts were associated with high harm avoidance (β = 0.322, P < .001, and β = 0.184, P = .062, respectively) and low reward dependence (β = -0.274, P < .001, and β = -0.134, P = .196, respectively), cooperativeness (β = -0.181, P = .005, and β = -0.096, P = .326, respectively), and novelty seeking (β = -0.137, P = .047). No association remained significant when only prospective suicide attempts during MDEs were included. After adjustment was made for total time spent in MDEs, only high persistence predicted suicide attempts (β = 0.190, P < .05). Formal mediation analyses of harm avoidance and self-directedness on prospectively ascertained suicide attempts indicated significant mediated effect through time at risk in MDEs, but no significant direct effect. CONCLUSIONS Among mood disorder patients, suicide attempt risk is associated with temperament and character dimensions. However, their influence on predisposition to suicide attempts is likely to be mainly indirect, mediated by more time spent in depressive episodes.

Local non-linear interactions in the visual cortex may reflect global decorrelation

The classical receptive field in the primary visual cortex have been successfully explained by sparse activation of relatively independent units, whose tuning properties reflect the statistical dependencies in the natural environment. Robust surround modulation, emerging from stimulation beyond the classical receptive field, has been associated with increase of lifetime sparseness in the V1, but the system-wide modulation of response strength have currently no theoretical explanation. We measured fMRI responses from human visual cortex and quantified the contextual modulation with a decorrelation coefficient (d), derived from a subtractive normalization model. All active cortical areas demonstrated local non-linear summation of responses, which were in line with hypothesis of global decorrelation of voxels responses. In addition, we found sensitivity to surrounding stimulus structure across the ventral stream, and large-scale sensitivity to the number of simultaneous objects. Response sparseness across voxel population increased consistently with larger stimuli. These data suggest that contextual modulation for a stimulus event reflect optimization of the code and perhaps increase in energy efficiency throughout the ventral stream hierarchy. Our model provides a novel prediction that average suppression of response amplitude for simultaneous stimuli across the cortical network is a monotonic function of similarity of response strengths in the network when the stimuli are presented alone.

Is dispositional optimism or dispositional pessimism predictive of ideal cardiovascular health? The Young Finns Study

Objective: We examined the independent association between dispositional optimism compared to dispositional pessimism and ideal cardiovascular health (defined by the American Heart Association). Design: A prospective design with a study sample of 1113 participants aged 24–39 years from the longitudinal Young Finns Study. Main outcome measures: Ideal cardiovascular health (comprised of seven ideal cardiovascular health metrics) was measured in 2001. The ideal cardiovascular health metrics were reassessed in 2007. Results: Low pessimism rather than high optimism was a better predictor of ideal cardiovascular health in 2007. When examining the association between optimism and pessimism and the seven ideal cardiovascular health metrics in 2007 (BMI, diet, physical activity, smoking status, blood pressure, total cholesterol and plasma glucose), low pessimism predicted non-smoking status, ideal physical activity and eating a healthy diet, while high optimism was associated with eating a healthy diet. Conclusion: Our findings suggest that low pessimism rather than high optimism is associated with ideal cardiovascular health, especially with health behaviours such as not smoking, being physically active and eating a healthy diet. Socio-economic status was the potential mediating or confounding factor. Future studies should examine the differential meaning of the optimism/pessimism concepts to further clarify their relation to health outcomes.