Nikolai Olavi Czajkowski

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CONTEXT Although both genetic and environmental factors affect risk of individual personality disorders (PDs), we know little of how they contribute to the pattern of comorbidity between the PDs in the Diagnostic and Statistical Manual of Mental Disorders (Fourth Edition) (DSM-IV). OBJECTIVE To clarify the structure of the genetic and environmental risk(More)
BACKGROUND The personality disorders (PDs) in the 'dramatic' cluster B [antisocial (ASPD), histrionic (HPD), narcissistic (NPD) and borderline (BPD)] demonstrate co-morbidity. However, the degree to which genetic and/or environmental factors influence their co-occurrence is not known and, with the exception of ASPD, the relative impact of genetic and(More)
OBJECTIVE To estimate the heritability of tinnitus. DESIGN Self-report questionnaire data collected from August 1, 1995, through June 30, 1997, from individuals in the Nord-Trøndelag Hearing Loss Study (an integrated part of the Nord-Trøndelag Health Study) were used. The study also included information on first-degree family relationships, and(More)
BACKGROUND The DSM-IV cluster C Axis II disorders include avoidant (AVPD), dependent (DEPD) and obsessive-compulsive (OCPD) personality disorders. We aimed to estimate the genetic and environmental influences on dimensional representations of these disorders and examine the validity of the cluster C construct by determining to what extent common familial(More)
BACKGROUND The extent to which positive and negative indicators of mental health share etiological influences has been studied to a limited degree only. This study examines the genetic and environmental influences on association between liability to lifetime DSM-IV Major Depressive Disorder (MDD) and dispositional life satisfaction (LS). METHODS Two-wave(More)
Lack of control of confounding variables, high attrition rate, and too few neurocognitive domains completed at each assessment point are some of the limitations identified in studies of the relationship between cognition and functional outcome in schizophrenia. In the ongoing Oslo multi-follow-up study 28 first episode schizophrenia patients and a pairwise(More)
BACKGROUND The 'odd' or 'Cluster A' personality disorders (PDs) - paranoid, schizoid and schizotypal PDs - were created in DSM-III with little empirical foundation. We have examined the relationship between the genetic and environmental risk factors for dimensional representations of these three personality disorders. METHOD These personality disorders(More)
OBJECTIVE One of the most important controversies regarding depressive personality disorder is the overlap with mood disorders. The aim of this study was to estimate the genetic and environmental sources of covariance between depressive personality disorder and major depressive disorder and to what extent genetic, shared, and unique environmental factors(More)
BACKGROUND Depressive personality disorder (DPD) was introduced in DSM-IV as a new category requiring further study. The aim of this study was to estimate genetic and environmental contributions to DPD in a population-based twin sample, and include data on criteria performance, prevalence and diagnostic overlap. METHODS Axis I and Axis II diagnoses were(More)
IMPORTANCE Previous studies have indicated that the psychopathological dimensions of borderline personality disorder (BPD) are influenced by a unitary liability factor. However, to our knowledge, the underlying etiological nature of the individual criteria for BPD as defined by the DSM-IV has not been explored. OBJECTIVE To determine the structure of(More)