Biomedical subjects

Michael Höfler

Publications and source records attributed to Michael Höfler.

At least 19 recordsLinked to original sources

PubMed2007

Childhood separation anxiety and the risk of subsequent psychopathology: Results from a community study.

OBJECTIVE: To examine the association between separation anxiety disorder (SAD) and mental disorders in a community sample and to evaluate whether separation anxiety is specifically related to panic disorder with and without agoraphobia. METHOD: The data come from a 4-year, prospective longitudinal study of a representative cohort of adolescents and young adults aged 14-24 years at baseline in Munich, Germany. The present analyses are based on a subsample of the younger cohort that completed baseline and two follow-up investigations (n = 1,090). DSM-IV diagnoses were made using the Munich Composite International Diagnostic Interview. Cox regressions with time-dependent covariates were used to examine whether prior SAD is associated with an increased risk for subsequent mental disorders. RESULTS: Participants meeting DSM-IV criteria for SAD were at an increased risk of developing subsequent panic disorder with agoraphobia (PDAG) (HR = 18.1, 95% CI = 5.6-58.7), specific phobia (HR = 2.7, 95% CI = 1.001-7.6), generalized anxiety disorder (HR = 9.4, 95% CI = 1.8-48.7), obsessive-compulsive disorder (HR = 10.7, 95% CI = 1.7-66.1), bipolar disorder (HR = 7.7, 95% CI = 2.8-20.8), pain disorder (HR = 3.5, 95% CI = 1.3-9.1), and alcohol dependence (HR = 4.7, 95% CI = 1.7-12.4). Increased hazard rates for PDAG (HR = 4.2, 95% CI = 1.4-12.1), bipolar disorder type II (HR = 8.1, 95% CI = 2.3-27.4), pain disorder (HR = 1.9, 95% CI = 1.01-3.5), and alcohol dependence (HR = 2.1, 95% CI = 1.1-4.) were also found for subjects fulfilling subthreshold SAD. CONCLUSIONS: Although revealing a strong association between SAD and PDAG, our results argue against a specific SAD-PDAG relationship. PDAG was neither a specific outcome nor a complete mediator variable of SAD.

Adolescent↗

PubMed2006

Re-interpreting conventional interval estimates taking into account bias and extra-variation.

BACKGROUND: The study design with the smallest bias for causal inference is a perfect randomized clinical trial. Since this design is often not feasible in epidemiologic studies, an important challenge is to model bias properly and take random and systematic variation properly into account. A value for a target parameter might be said to be "incompatible" with the data (under the model used) if the parameter's confidence interval excludes it. However, this "incompatibility" may be due to bias and/or extra-variation. DISCUSSION: We propose the following way of re-interpreting conventional results. Given a specified focal value for a target parameter (typically the null value, but possibly a non-null value like that representing a twofold risk), the difference between the focal value and the nearest boundary of the confidence interval for the parameter is calculated. This represents the maximum correction of the interval boundary, for bias and extra-variation, that would still leave the focal value outside the interval, so that the focal value remained "incompatible" with the data. We describe a short example application concerning a meta analysis of air versus pure oxygen resuscitation treatment in newborn infants. Some general guidelines are provided for how to assess the probability that the appropriate correction for a particular study would be greater than this maximum (e.g. using knowledge of the general effects of bias and extra-variation from published bias-adjusted results). SUMMARY: Although this approach does not yet provide a method, because the latter probability can not be objectively assessed, this paper aims to stimulate the re-interpretation of conventional confidence intervals, and more and better studies of the effects of different biases.

Bias↗

PubMed2006

Getting causal considerations back on the right track.

In their commentary on my paper Phillips and Goodman suggested that counterfactual causality and considerations on causality like those by Bradford Hill are only "guideposts on the road to common sense". I argue that if common sense is understood to mean views that the vast majority of researchers share, Hill's considerations did not lead to common sense in the past--precisely because they are so controversial. If common sense is taken to mean beliefs that are true, then Hill's considerations can only lead to common sense in the simple and well-understood causal systems they apply to. Counterfactuals, however, are largely common sense in the latter meaning.I suggest that the road of scientific endeavour should lead epidemiologic research toward sound strategies that equip researchers with skills to separate causal from non-causal associations with minimal error probabilities. This is undeniably the right direction and the one counterfactual causality leads to. Hill's considerations are merely heuristics with which epidemiologists may or may not find this direction, and they are likely to fail in complex landscapes (causal systems). In such environments, one might easily lose orientation without further aids (e.g., defendable assumptions on biases). Counterfactual causality tells us when and how to apply these heuristics.

Comment↗

PubMed2006

Where have they been? Service use of regular substance users with and without abuse and dependence.

OBJECTIVE: To present lifetime rates of service use for psychological and substance use related problems among regular substance users and to examine factors associated with service use. METHOD: Data come from a prospective-longitudinal, epidemiological study of a community sample of adolescents and young adults (n = 2548, age 14-24 years at baseline) in Munich, Germany. The Munich-Composite International Diagnostic Interview (M-CIDI) was used at baseline and at two follow-ups to assess substance use and service use. RESULTS: Cumulated lifetime incidence of any substance abuse or dependence was 43.7%. Of those with abuse and dependence 23% had ever used any services for psychological or substance use related problems. Illicit substance users especially those with dependence had the highest rates of lifetime service use (52.1%). Psychotherapists and counseling services were contacted most frequently among regular substance users over their lifetimes. Utlilisation rates of substance abuse services were low (2%). Comorbid anxiety disorders and distressing life events were associated with increased lifetime service use. CONCLUSIONS: Only a minority of adolescents and young adults with substance use disorders have ever sought professional help. Specialized substance abuse services play only a minor role. The core role of psychotherapists and non-substance abuse specialized services needs critical research attention. Linkages between psychotherapists and the substance use service system should be strengthened to detect and intervene at early developmental stages of abuse and dependence.

Adolescent↗

PubMed2006

Clinical characteristics of major depressive disorder run in families--a community study of 933 mothers and their children.

The familial aggregation of Major Depressive Disorder (MDD) has been repeatedly demonstrated. Several studies have investigated associations between various clinical characteristics of MDD in probands and overall rates of MDD in relatives. Few studies, however, have considered the familial aggregation of clinical characteristics of MDD. The aim of the present report is to examine mother-offspring associations of a variety of clinical characteristics of MDD in a general population sample. Data were derived from baseline and 4-year-follow-up data of 933 adolescents and their biological mothers of the Early Developmental Stages of Psychopathology (EDSP) study, a prospective-longitudinal community study. MDD and its characteristics were assessed with the Munich-Composite International Diagnostic Interview. We found that children of mothers who had a lifetime history of severe MDD and high number of symptoms, high impairment and/or melancholia, revealed elevated odds of MDD regarding the same characteristics as their mothers (ORs between 5.2 and 13.9). The observed associations did not differ by the children's sex. DSM-IV melancholia and severity as well as impairment were found to aggregate within families. This finding can be interpreted as a validation of the DSM-IV MDD severity subtypes as well as of the melancholic specifier. Severe and melancholic MDD reveal a considerable high degree of familiar aggregation making the search for mechanisms involved in the familiar transmission of these forms of MDD particularly promising.

Adolescent↗

PubMed2006

Different results on tetrachorical correlations in Mplus and Stata--Stata announces modified procedure.

To identify the structure of mental disorders in large-scale epidemiological data sets, investigators frequently use tetrachoric correlations as a first step for subsequent application of latent class and factor analytic methods. It has been possible to do this with Stata since 2005, whereas the corresponding Mplus routine has been on the market for some years. Using an identical data set we observed considerable differences between the results of the packages. This paper illustrates the differences with several examples from the Early Developmental Stages of Psychopathology Study data set, which consists of 3021 subjects, with diagnostic information assessed by the CIDI. Results reveal that tetrachoric correlations resulting from Mplus were often considerably smaller than those computed with Stata. The results were dramatically different, especially where there were few observation per cell or even empty cells. These findings were put to Mplus and Stata, whose responses clarified the discrepancies by describing the different mathematical assumptions and procedures used. Stata announced that it intended to launch a modified procedure.

Computer Simulation↗

PubMed2006

High cholesterol, triglycerides, and body-mass index in suicide attempters.

Low cholesterol concentrations and cholesterol-lowering therapies have been suggested to be associated with increased suicidality. This article examined the association of cholesterol, triglycerides, and body-mass index (BMI) with suicidal ideation and suicide attempts. Findings are based on a nationally representative community sample of n = 4,181 subjects (18-65 years) examined with a standardized diagnostic interview (CIDI) for (DSM-IV) mental disorders. Controlling for age and gender the study revealed a moderate positive association between cholesterol, triglycerides, BMI, and suicide attempts in subjects with depressive symptoms during the past 12 months (n = 1,205). The results of this study are compatible with two recent epidemiological cohort studies showing a positive association between cholesterol and completed suicide.

Adolescent↗

PubMed2005

The Bradford Hill considerations on causality: a counterfactual perspective.

Bradford Hill's considerations published in 1965 had an enormous influence on attempts to separate causal from non-causal explanations of observed associations. These considerations were often applied as a checklist of criteria, although they were by no means intended to be used in this way by Hill himself. Hill, however, avoided defining explicitly what he meant by "causal effect". This paper provides a fresh point of view on Hill's considerations from the perspective of counterfactual causality. I argue that counterfactual arguments strongly contribute to the question of when to apply the Hill considerations. Some of the considerations, however, involve many counterfactuals in a broader causal system, and their heuristic value decreases as the complexity of a system increases; the danger of misapplying them can be high. The impacts of these insights for study design and data analysis are discussed. The key analysis tool to assess the applicability of Hill's considerations is multiple bias modelling (Bayesian methods and Monte Carlo sensitivity analysis); these methods should be used much more frequently.

Journal Article↗

PubMed2005

Calculating control variables with age at onset data to adjust for conditions prior to exposure.

BACKGROUND: When assessing the association between a factor X and a subsequent outcome Y in observational studies, the question that arises is what are the variables to adjust for to reduce bias due to confounding for causal inference on the effect of X on Y. Disregarding such factors is often a source of overestimation because these variables may affect both X and Y. On the other hand, adjustment for such variables can also be a source of underestimation because such variables may be the causal consequence of X and part of the mechanism that leads from X to Y. METHODS: In this paper, we present a simple method to compute control variables in the presence of age at onset data on both X and a set of other variables. Using these age at onset data, control variables are computed that adjust only for conditions that occur prior to X. This strategy can be used in prospective as well as in survival analysis. Our method is motivated by an argument based on the counterfactual model of a causal effect. RESULTS: The procedure is exemplified by examining of the relation between panic attack and the subsequent incidence of MDD. CONCLUSIONS: The results reveal that the adjustment for all other variables, irrespective of their temporal relation to X, can yield a false negative result (despite unconsidered confounders and other sources of bias).

Adolescent↗

PubMed2005

Pathways into ecstasy use: the role of prior cannabis use and ecstasy availability.

AIM: To explore the role of cannabis use for the availability of ecstasy as a potential pathway to subsequent first ecstasy use. METHODS: Baseline and 4-year follow-up data from a prospective-longitudinal community study of originally 3021 adolescents and young adults aged 14-24 years at baseline were assessed using the standardized M-CIDI and DSM-IV criteria. RESULTS: Baseline cannabis users reported at follow-up more frequent access to ecstasy than cannabis non-users. Higher cannabis use frequencies were associated with increased ecstasy availability reports. Logistic regression analyses revealed that cannabis use and availability of ecstasy at baseline are predictors for incident ecstasy use during the follow-up period. Testing simultaneously the impact of prior cannabis use and ecstasy availability including potential confounders, the association with cannabis use and later ecstasy use was confirmed (OR=6.3; 95%CI=3.6-10.9). However, the association with ecstasy availability was no longer significant (OR=1.2; 95%CI=0.3-3.9). CONCLUSIONS: Results suggest that cannabis use is a powerful risk factor for subsequent first onset of ecstasy use and this relation cannot be sufficiently explained by availability of ecstasy in the observation period.

Adolescent↗

PubMed2005

The effect of misclassification on the estimation of association: a review.

Misclassification, the erroneous measurement of one or several categorical variables, is a major concern in many scientific fields and particularly in psychiatric research. Even in rather simple scenarios, unless the misclassification probabilities are very small, a major bias can arise in estimating the degree of association assessed with common measures like the risk ratio and the odds ratio. Only in very special cases--for example, if misclassification takes place solely in one of two binary variables and is independent of the other variable ('non-differential misclassification')--is it guaranteed that the estimates are biased towards the null value (which is 1 for the risk ratio and the odds ratio). Furthermore, misclassification, if ignored, usually leads to confidence intervals that are too narrow. This paper reviews consequences of misclassification. A numerical example demonstrates the problem's magnitude for the estimation of the risk ratio in the easy case where misclassification takes place in the exposure variable, but not in the outcome. Moreover, uncertainty about misclassification can broaden the confidence intervals dramatically. The best way to overcome misclassification is to avoid it by design, but some statistical methods are useful for reducing bias if misclassification cannot be avoided.

Association↗

PubMed2005

The use of weights to account for non-response and drop-out.

BACKGROUND: Empirical studies in psychiatric research and other fields often show substantially high refusal and drop-out rates. Non-participation and drop-out may introduce a bias whose magnitude depends on how strongly its determinants are related to the respective parameter of interest. METHODS: When most information is missing, the standard approach is to estimate each respondent's probability of participating and assign each respondent a weight that is inversely proportional to this probability. This paper contains a review of the major ideas and principles regarding the computation of statistical weights and the analysis of weighted data. RESULTS: A short software review for weighted data is provided and the use of statistical weights is illustrated through data from the EDSP (Early Developmental Stages of Psychopathology) Study. The results show that disregarding different sampling and response probabilities can have a major impact on estimated odds ratios. CONCLUSIONS: The benefit of using statistical weights in reducing sampling bias should be balanced against increased variances in the weighted parameter estimates.

Adolescent↗

PubMed2005

Mania, hypomania, and suicidality: findings from a prospective community study.

We examined prospectively whether mania and hypomania are associated with an elevated risk for suicidality in a community sample of adolescents and young adults. Baseline and four-year follow-up data were used from the Early-Developmental-Stages-of-Psychopathology (EDSP) Study, a prospective longitudinal study of adolescents and young adults in Munich. Suicidal tendencies (ideation/attempts), mania, and hypomania were assessed using the standardized Munich-Composite-International-Diagnostic-Interview. At baseline, mania/hypomania was associated to a different degree with suicidality (Odds ratios [OR] range from 1.9 to 13.7). In the prospective analyses, the risk for subsequent incident suicidal ideation was increased in the presence of prior mania (38.0% vs. 14.1%; OR = 4.4; 95% CI = 1.4-13.5). No associations could be found between prior mania/hypo-mania and incident suicide attempts. The prospective analyses revealed a remarkable relationship between preexisting mania and increased risk for subsequent suicidal ideation.

Adolescent↗

PubMed2005

Longitudinal course of posttraumatic stress disorder and posttraumatic stress disorder symptoms in a community sample of adolescents and young adults.

OBJECTIVE: Few studies have focused on the natural course of posttraumatic stress disorder (PTSD) and its determinants in samples of the general population. The authors examined determinants of remission and chronicity of PTSD and associations with other disorders in a prospective community sample. METHOD: The data were drawn from a prospective, longitudinal epidemiological study of adolescents and young adults (age 14-24 years) in Munich, Germany (N=2,548). The course of PTSD from baseline to follow-up 34-50 months later was studied in 125 respondents with DSM-IV PTSD or subthreshold PTSD at baseline. RESULTS: Although 52% of the PTSD cases remitted during the follow-up period, 48% showed no significant remission of PTSD symptoms. Respondents with a chronic course were more likely to experience new traumatic event(s) during follow-up (odds ratio=5.21, 95% confidence interval [CI]=1.95-13.92), to have higher rates of avoidant symptoms at baseline (odds ratio=10.16, 95% CI=1.73-59.51), and to report more help seeking (odds ratio=5.50, 95% CI=1.04-29.05), compared to respondents with remission. Rates of incident somatoform disorder (odds ratio=4.24, 95% CI=1.60-11.19) and other anxiety disorders (odds ratio=4.07, 95% CI=1.15-14.37) were also significantly associated with a chronic course. CONCLUSIONS: PTSD is often a persistent and chronic disorder. Specific symptom clusters--especially avoidant symptoms--might be associated with the course of PTSD. In addition, the occurrence of new traumatic events differentiates PTSD cases with a chronic course from those with remission.

Adolescent↗

PubMed2005

Maternal suicidality and risk of suicidality in offspring: findings from a community study.

OBJECTIVE: This study evaluated the associations between suicidal ideation and suicide attempts in mothers and various aspects of suicidality in their offspring in a representative community sample. METHOD: Baseline and 4-year follow-up data were used from the Early Developmental Stages of Psychopathology study, a prospective, longitudinal community study of adolescents and young adults. Results are based on 933 adolescents who completed follow-up and for whom direct diagnostic information for the biological mother was available. Suicidal ideation and suicide attempts were assessed in adolescents and mothers with the Munich-Composite International Diagnostic Interview. RESULTS: Compared to offspring of mothers without suicidality, offspring of mothers reporting suicide attempts showed a remarkably higher risk for suicidal thoughts and suicide attempts and a tendency toward suicide attempts at an earlier age. Associations were comparable for male and female offspring. Transmission of maternal suicidality was roughly stable with control for maternal comorbid psychopathology. CONCLUSIONS: The offspring of mothers with suicide attempts are at a markedly increased risk for suicidality themselves and tend to manifest suicide attempts earlier than offspring of mothers without suicidality. Suicidality seems to run in families, independent of depression and other psychopathology.

Adolescent↗

PubMed2004

[The use of guidelines in the primary care management of hypertension and diabetes].

OBJECTIVES: The paper examines to what degree German primary care physicians know and work along the rules established in guidelines for arterial hypertension and diabetes mellitus. METHODS: HYDRA is a 2-stage cross-sectional point prevalence study with 1912 participating primary care settings throughout Germany including 45,125 patients. A pre-study questionnaire to assess doctors practice patterns was used. Subsequently doctors completed a structured clinical appraisal with a diagnostic workup and characterization of the current treatments provided. All patients filled out a questionnaire. RESULTS: Pre-study results show that only every second primary care physician manages the patients according to established guidelines. Further, physicians estimated their own work as problematic and not always successful. Guideline-oriented doctors were more likely to report hypertension and diabetes treatment patterns that also match guideline's recommendations. CONCLUSIONS: The study shows a considerable degree of dissatisfaction with the quality of their work among primary care physicians. Guideline-oriented doctors however reveal more frequently formally adequate management characteristics. This encouraging aspect suggests the need of more successful implementation of medical guidelines in order to achieve improved evidence-based medicine and better patient-oriented health care.

Adult↗

PubMed2004

HYDRA: possible determinants of unsatisfactory hypertension control in German primary care patients.

The Hypertension and Diabetes Screening and Awareness (HYDRA) study is a cross-sectional point-prevalence study performed in September 2001; 45,125 primary care attendees were recruited from a representative nationwide sample of 1912 primary care practices in Germany. Around 42% of all patients presenting in these practices had hypertension (WHO definition). In approximately 70% of these patients, hypertension was diagnosed by doctors and 84% of diagnosed patients were on antihypertensive medication, but in less than 30% of treated patients was blood pressure controlled (< 140/90 mmHg). The control rate in all patients presenting with hypertension (including those patients unrecognized) was as low as 19%. The present analysis aimed to find explanations for this unsatisfactory outcome of hypertension control. The main finding was that the rate of diagnosis of hypertension is alarmingly low in young people, probably due to insufficient blood pressure screenings. The data further indicated that doctors still set their target of treatment according to outdated guidelines and that doctors still orientate their treatment primarily with regard to the diastolic pressure. These insights into the causes of unsatisfactory hypertension control may help to direct future educational programmes designed to improve hypertension management specifically to these deficits and thereby to improve control rates.

Adolescent↗

PubMed2004

High prevalence and poor control of hypertension in primary care: cross-sectional study.

OBJECTIVE: To report: (1) on the background, design and methods of the Hypertension and Diabetes Risk Screening and Awareness (HYDRA) study, (2) on the point prevalence of hypertension in primary care and (3) on the proportion of treated, controlled, and uncontrolled hypertension. DESIGN: Cross-sectional point prevalence study. SETTING: Representative nationwide sample of 1912 primary care practices in Germany. PARTICIPANTS: A total of 45,125 unselected primary care attendees. MAIN OUTCOME MEASURES: Prevalence of hypertension based on doctor's diagnosis, self-reported diagnosis, and blood pressure (BP) measurements. RESULTS: A total of 39% of all patients and 67% of patients aged 60 years or older, respectively, were diagnosed by their doctors as having hypertension. Eighty-four percent of diagnosed patients were on antihypertensive medication, 57% of which were rated by the physician as well controlled. When hypertension was defined as either current BP levels > or = 140/90 mmHg and/or current antihypertensive medication, the total point prevalence increased to 50%, while treatment and control rates (BP < 140/90 mmHg) dropped to 64 and 19%, respectively. CONCLUSIONS: Extrapolation of these findings to the entire primary care patient population seen in the over 20 000 primary care practices in Germany suggests that on an average day, over 700,000 patients with elevated BP are seen by primary care physicians, but that only around 132,000 of these patients are well controlled. Thus, this study not only documents the enormous burden of hypertensive patients in the primary health system, but also highlights the alarming lack of BP control in the vast majority of hypertensive patients.

Adolescent↗