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C O Gardner

Publications and source records attributed to C O Gardner.

At least 19 recordsLinked to original sources
PubMed2003

Interpersonal dependence and major depression: aetiological inter-relationship and gender differences.

BACKGROUND: Although prior research has demonstrated a strong association between interpersonal dependency (IPD) levels and risk for major depression (MD), the possible aetiological explanations of this association as well as any gender differences in the IPD-MD relationship need further clarification. METHOD: Population-based twin samples (N = 7174) were interviewed in multiple waves to assess IPD and MD as part of a larger twin study. IPD levels were assessed using the Interpersonal Dependency Inventory while MD diagnoses were derived from the SCID. Cox proportional hazard models and multiple regression techniques were utilized. RESULTS: IPD was strongly associated with a risk for lifetime MD. Pre-morbid IPD scores were predictive of future onsets of MD while experiencing a MD episode was also associated with a significant rise in IPD levels. While females had higher IPD scores, IPD scores were more significantly associated with risk for lifetime MD in males. Controlling for the level of IPD substantially reduced the observed association between gender and risk for MD. CONCLUSION: The strong association observed between IPD and risk for MD results largely from IPD being a risk factor for MD, but state effects of MD on IPD also contribute. IPD scores in males were more predictive of lifetime MD than for females. The higher levels of IPD in women than in men may contribute meaningfully to the sex differences in risk for MD.

Major Depressive Disorder↗
PubMed2003

Personality and the experience of environmental adversity.

BACKGROUND: While psychiatric epidemiology often focuses on the causal relationship between environmental adversity and the individual (e.g. environment to person), individuals probably make important contributions to the quality of their environments (person to environment). METHOD: In a population based sample of > 7000 male and female adult twins, we examined the relationship between the personality trait of neuroticism (N) and the occurrence of stressful life events (SLEs) and the quality of interpersonal relationships (IPR). We compared the magnitude of the prediction of twin 1's self-reported SLEs and IPR from: (i) twin 1's self-reported N; (ii) twin 2's report of twin 1's N; and (iii) twin 2's report of twin 2's N in monozygotic pairs. RESULTS: In our entire sample, self-report N significantly predicted the occurrence of most SLEs and all dimensions of IPR. Using the co-twin's report of N produced associations that were of the same magnitude for SLEs and modestly weaker for IPR. In monozygotic pairs, the level of N in one twin predicted SLEs and IPR in the co-twin at levels similar to those found for the co-twin's report of N. Repeating these analyses with a prospective subsample produced similar results. CONCLUSION: An individual's personality in adulthood plays a significant role in influencing exposure to some forms of environmental adversity and this association is not the result of reporting bias. Furthermore, this relationship is largely mediated by a common set of familial factors that predispose both to a 'difficult' temperament and to environmental adversity. Developmental models of psychiatric illness should adopt an interactionist view of individuals and their environment (person and environment).

Adaptation, Psychological↗
PubMed2002

Neuroticism, major depression and gender: a population-based twin study.

BACKGROUND: A portion of the genetic risk factors for the personality trait neuroticism (N) may also increase risk for major depression (MD). Females have both higher levels of N and higher rates of MD than males, suggesting that these traits may be more genetically correlated in females. METHODS: Structured interviews, including a lifetime assessment for MD by DSM-III-R criteria, were administered to 863 male-male MZ (monozygotic), 649 male-male DZ (dizygotic), 506 female-female MZ, 345 female-female DZ, and 1,408 opposite-sex twin pairs. N was assessed using the short-form of the Eysenck Personality Questionnaire. A sex-limited Cholesky model was fitted which allowed us to decompose into additive genetic, common environmental, and individual-specific environmental components two main classes of correlations: within-sex between-variable and between-sex within-variable. RESULTS: Our best-fitting model contained only additive genetic and individual-specific environmental factors for both N and MD. The within-sex genetic correlations between N and MD were estimated at +0.68 in men and +0.49 in women. This model fitted only slightly better than one in which the N-MD within-sex genetic correlation was constrained to be equal across the sexes, and estimated at +0.55. There may be sex-specific genes influencing both N and MD. CONCLUSION: Our best-fitting model failed to establish a significant sex difference in the genetic correlation between N and MD. These results, as well as evidence for sex-specific genetic factors for both traits, have implications for the diagnosis, classification, and treatment of the affective disorders, and molecular genetic approaches to the study of these traits.

Adult↗
PubMed2002

Childhood parental loss and risk for first-onset of major depression and alcohol dependence: the time-decay of risk and sex differences.

BACKGROUND: Whereas a number of studies have suggested that parental loss is associated with increased risk for major depression (MD), much less is known about possible gender differences, diagnostic specificity and the time course of the impact of loss. METHOD: First-onsets for MD and alcohol dependence (AD) were assessed at personal interviews in 5070 twins from same-sex (SS) and 2118 from opposite-sex (OS) twin pairs ascertained from a population-based registry. Cox Proportional Hazard (PH) and Non-Proportional Hazard (NPH) models, examining first onsets of MD and AD, were used with twins from SS pairs and conditional logistic regression for OS pairs. Parent-child separations prior to age 17 were divided into death and separation from other causes. RESULTS: The PH assumptions of constant increased risk were rejected for the impact of loss on risk for MD but not for AD. NPH models found significantly increased risk for MD after both death and separation with the risk lasting much longer for separations. For AD, the PH model found significantly increased risk after parental separation but not death. In both SS and OS twin pairs, no sex differences were seen in the impact of parental loss on risk for MD whereas the association between separation and risk for AD was significantly stronger in females than in males. CONCLUSION: Consistent sex differences in the association with parental loss were seen for AD but not MD. The analysis of the time-course of increased risk after loss suggests three different patterns which may reflect different relationships: parental death and MD (return to baseline within approximately 12 years), separation and MD (return to baseline within approximately 30 years) and separation and AD (no change in risk over time).

Age of Onset↗
PubMed2001

Monozygotic twins discordant for major depression: a preliminary exploration of the role of environmental experiences in the aetiology and course of illness.

BACKGROUND: Genetic effects upon behaviour are pervasive. To what extent are the many correlates of major depression (MD) due to individual-specific environmental experiences versus genetic factors correlated with risk for MD? METHODS: From a population-based twin registry, we identified 72 female monozygotic pairs discordant for a lifetime history of MD and compared the affected and unaffected members on a wide range of putative correlates of MD. RESULTS: The affected twin differed from her unaffected co-twin on many variables, eight of which were maximally discriminating: (i) maternal protectiveness; (ii) conflictual parent-child relationship; (iii) low optimism; (iv) current stressful life events; (v) financial difficulties and a history of (vi) phobia, (vii) nicotine dependence; and (viii) divorce. A cluster analysis suggested three 'environmental pathways' to MD characterized by: (i) childhood vulnerability and anxiety; (ii) acting-out and demoralization; and (iii) interpersonal difficulties. CONCLUSION: Important precursors and sequelae of MD originate in environmental experiences unique to the individual and are not mediated through genetic factors or family-of-origin effects. Such environmental factors cause pervasive differences in monozygotic twins discordant for MD, especially in the areas of interpersonal difficulties, psychopathology, social problems and self-concept. These findings should be interpreted in the context of possible retrospective recall bias and the difficulty of distinguishing risk factors from sequelae in co-twin-control studies.

Adult↗
PubMed2001

Are there sex differences in the reliability of a lifetime history of major depression and its predictors?

BACKGROUND: Although lifetime major depression (LTMD) is assessed with only moderate reliability in community samples, some predictors have emerged for 'reliable' LTMD. Given the large impact of sex on risk for LTMD, it is of interest to know if there are sex differences in the reliability of LTMD and its predictors. METHODS: A total of 5603 members of male-male and male-female twin pairs from a population-based registry were interviewed twice with a mean inter-interview interval of 19 months. LTMD was assessed on each occasion using DSM-III-R criteria. Univariate and multivariate logistic regression analyses were used, combining forward and back-prediction. RESULTS: The long-term test-retest reliability of LTMD was moderate (kappa = +0.48) and did not differ significantly between males and females. In a multivariate model, the significant predictors of a stable diagnosis of LTMD, none of which differed across sex, were younger age at onset, older current age, history of treatment, increasing number of symptoms, level of impairment or level of distress, longer duration of episodes, higher current level of depression and the presence during the depressive episode of sad mood, weight loss, hypersomnia or fatigue. Using these variables, it was not possible to predict 'stably diagnosed' LTMD with both high sensitivity and high specificity. CONCLUSION: In community samples, LTMD is diagnosed with moderate reliability. Although diagnostic stability can be predicted by variables related to severity, distress and treatment-seeking (probably acting to make depressive episodes more 'memorable'), highly accurate prediction of stably diagnosed cases is not possible. Long-term recall is also significantly influenced by current symptoms. Neither the stability of LTMD nor its predictors differ in men and women.

Adult↗
PubMed2001

Genetic risk factors for major depression in men and women: similar or different heritabilities and same or partly distinct genes?

BACKGROUND: Although women are at consistently greater risk for major depression (MD) than men, it is unclear whether sex modifies the aetiological impact of genetic factors on MD. Is the heritability of MD different in men and women? Do the same genetic risk factors predispose to MD in the two sexes? METHODS: We obtained a lifetime history of MD by personal interview on two occasions from 6672 individual twins and 2974 complete twin pairs. Three diagnostic criteria of increasing narrowness were employed: DSM-III-R, DSM-III-R plus impairment and Washington University. To increase power by controlling for unreliability of assessment, we evaluated sex differences on genetic risk for MD using a structural equation measurement model. RESULTS: Using DSM-III-R criteria, but not the two narrower definitions, heritability of MD was significantly greater in women than in men. In the three diagnostic systems, the genetic correlation in liability to MD in men and women was estimated at between +0.50 and +0.65. These estimates differed significantly from unity for the two broader definitions. CONCLUSION: Using broad but not narrower definitions of illness, genetic factors play a greater role in the aetiology of MD in women than in men. The genes that influence risk for MD in the two sexes are correlated but are probably not entirely the same. These results raise the possibility that, in linkage and association studies, the impact of some loci on risk for MD will differ in men and women.

Adult↗
PubMed2001

Panic syndromes in a population-based sample of male and female twins.

BACKGROUND: The risk for panic disorder (PD) is substantially increased in relatives of probands with PD. Prior literature provides only limited information about the degree to which this increase is due to genetic factors or family environment. METHODS: In personal interviews with both members of 3194 twin pairs, we assessed the lifetime history of lifetime panic attacks and PD. Twin resemblance was assessed by tetrachoric correlation and single and multiple threshold biometrical model fitting. RESULTS: As fully syndromal PD, by DSM-III-R criteria, was too rare to analyse usefully we examined four other dichotomous definitions of increasing stringency: panic probe and very broad, broad and intermediate PD. For all four definitions and for the multiple threshold analyses, the best-fit model indicated that twin resemblance was due solely to genetic factors with a moderate heritability (33-43%). For the broad and intermediate dichotomous definitions of PD, however, a model with twin resemblance due to familial-environmental factors fit nearly as well. No gender effects were seen on the genetic risk factors for these PD-like syndromes. CONCLUSION: Even with large epidemiological samples of twins, studying disorders as uncommon as PD is problematical. Despite these difficulties, our results suggest that: (i) narrowly and broadly defined PD are probably on the same continuum of liability; (ii) twin resemblance for these PD-like syndromes is likely due largely to genetic factors with a moderate level of heritability although a contribution of familial-environmental factors cannot be excluded, and, (iii) the same familial risk factors impact. to a similar degree, on the liability to PD in males and females.

Adult↗
PubMed2001

Genetic risk, number of previous depressive episodes, and stressful life events in predicting onset of major depression.

OBJECTIVE: The association between stressful life events and the onset of major depression decreases as the number of previous depressive episodes increases. How do genetic risk factors for major depression impact on this "kindling" phenomenon? In particular, do those at high genetic risk exhibit an increase in the speed of kindling, or are they "prekindled"? METHOD: Using discrete-time survival analysis, the authors examined the interaction between genetic risk, number of previous depressive episodes, and life event exposure in the prediction of episodes of major depression in female-female twin pairs from a population-based registry. The twins were interviewed four times over a 9-year period, producing 92,521 person-months of exposure. RESULTS: The decline in the association between stressful life events and risk for major depression as the number of previous depressive episodes increased was strongest in those at low genetic risk and was weak to absent in those at high genetic risk. In the absence of previous depressive episodes, those at high genetic risk frequently experienced depressive episodes without major environmental stressors. CONCLUSIONS: Genetic risk factors for depression produce a "prekindling" effect rather than increase the speed of kindling. The "kindled" state, wherein depressive episodes occur with little provocation, may be reached by two pathways: many previous depressive episodes, perhaps driven by multiple adversities, and high genetic risk.

Adult↗
PubMed2000

Obsessive and compulsive symptoms in a general population sample of female twins.

Obsessive-compulsive disorder (OCD) and obsessive-compulsive symptoms (OCS) exhibit a familial pattern of transmission. The different components of these conditions and the extent to which these components are inherited have not been studied well. A sample of 1,054 female twins, including both members of 527 pairs, from the Virginia Twin Registry returned questionnaires that included 20 items from the Padua Inventory of obsessive-compulsiveness. Their responses were used to estimate the heritability of the different factors of OCS in this population. Principal components analysis suggested two meaningful factors corresponding roughly to obsessions and compulsions. The best-fit model suggested heritabilities of 33 and 26%, respectively. The correlation between additive genetic effects on compulsiveness and obsessiveness was found to be +0.53. Self-report symptoms of obsessions and compulsions in women from the general population are moderately heritable and due, in part, to the same genetic risk factors. An understanding of the etiology of these symptoms is relevant to the study of OCD. Am. J. Med. Genet. (Neuropsychiatr. Genet.) 96:791-796, 2000.

Adult↗
PubMed2000

Stressful life events and previous episodes in the etiology of major depression in women: an evaluation of the "kindling" hypothesis.

OBJECTIVE: Although previous evidence has suggested that the etiologic role of stressful life events in major depression is reduced in recurrent versus first-onset cases, this question deserves reexamination because of potential methodological limitations of the previous studies. METHOD: Members of female-female twin pairs from a population-based registry (N=2,395), who were interviewed four times over a period of 9 years, formed a study group that contained 97,515 person-months and 1,380 onsets of major depression. Discrete-time survival, proportional hazards model, and piece-wise regression analyses were used to examine the interaction between life event exposure and number of previous depressive episodes in the prediction of episodes of major depression. RESULTS: For those with zero to nine previous depressive episodes, the depressogenic effect of stressful life events declined substantially with increasing episode number. However, the association between stressful life events and major depression was not substantially influenced by additional episodes. This pattern of results was robust to the addition of indices of event severity, measures of genetic risk, and restriction to independent stressful life events. The same pattern was also seen upon examining within-person changes in number of episodes. CONCLUSIONS: The association between previous number of depressive episodes and the pathogenic impact of stressful life events on major depression is likely causal and biphasic. Through approximately nine episodes, the association between stressful life event exposure and risk of major depression progressively declines but is largely unchanged with further episodes. These results are consistent with the kindling hypothesis but suggest a threshold at which the mind/brain is no longer additionally sensitized to the depressive state.

Adult↗
PubMed1999

Clinical characteristics of major depression that predict risk of depression in relatives.

BACKGROUND: Major depression (MD) is both clinically and etiologically heterogeneous. We attempt to relate clinical and etiologic heterogeneity by determining those features of MD that reflect a high familial liability to depressive illness. METHODS: Our sample, 3786 personally interviewed twin pairs from a population-based registry, contained 1765 people with a lifetime history of MD by DSM-III-R criteria, of whom 639 (36.2%) had affected co-twins. We examine, using Cox proportional hazard models, the clinical features of MD in affected twins that predicted the risk for MD in the co-twin. Control variables were zygosity, age at interview, and sex of the twin and co-twin. RESULTS: The best-fitting model contained 4 significant predictors: number of episodes, duration of longest episode, recurrent thoughts of death or suicide, and level of distress or impairment. These 4 clinical features were similarly predictive of the risk for MD in the co-twins of male and female twins and predicted risk of illness more strongly in monozygotic than in dizygotic twins. Variables that did not uniquely predict risk of MD in the co-twin included age at onset and number of depressive symptoms. For number of episodes, the best-fitting model indicated an inverted U-shaped function with greatest co-twin risk for MD with 7 to 9 lifetime episodes. CONCLUSIONS: The clinical features of MD in epidemiologic samples can be meaningfully related to the familial vulnerability to illness. Familial MD is best characterized by intermediate levels of recurrence, long duration of episodes, high levels of impairment, and recurrent thoughts of death or suicide. These clinical features probably reflect a high genetic liability to depressive illness.

Adult↗
PubMed1999

A population-based twin study in women of smoking initiation and nicotine dependence.

BACKGROUND: The development of drug dependence requires prior initiation. What is the relationship between the risk factors for initiation and dependence? METHODS: Using smoking as a model addiction, we assessed smoking initiation (SI) and nicotine dependence (ND) by personal interview in 1898 female twins from the population-based Virginia Twin Registry. We developed a twin structural equation model that estimates the correlation between the liability to SI and the liability to ND, given SI. RESULTS: The liabilities to SI and ND were substantially correlated but not identical. Heritable factors played an important aetiological role in SI and in ND. While the majority of genetic risk factors for ND were shared with SI, a distinct set of familial factors, which were probably partly genetic, solely influenced the risk for ND. SI was associated with low levels of education and religiosity, high levels of neuroticism and extroversion and a history of a wide range of psychiatric disorders. ND was associated with low levels of education, extroversion, mastery, and self-esteem, high levels of neuroticism and dependency and a history of mood and alcohol use disorders. CONCLUSIONS: The aetiological factors that influence SI and ND, while overlapping, are not perfectly correlated. One set of genetic factors plays a significant aetiological role in both SI and ND, while another set of familial factors, probably in part genetic, solely influences ND. Some risk factors for SI and ND impact similarly on both stages, some act at only one stage and others impact differently and even in opposite directions at the two stages. The pathway to substance dependence is complex and involves multiple genetic and environmental risk factors.

Adult↗
PubMed1999

Clarifying the relationship between religiosity and psychiatric illness: the impact of covariates and the specificity of buffering effects.

Previous analyses in a large population-based sample of female twins indicated that three dimensions of religiosity--personal devotion, personal conservatism and institutional conservatism--were, in different ways, significantly related to current depressive symptoms and substance use and lifetime psychiatric and substance use disorders. Furthermore, personal devotion, but neither personal conservatism nor institutional conservatism, buffered the depressogenic effects of stressful life events (SLEs). We here explore further these results, using linear, logistic and Cox regression models. Eight personality and six demographic variables had distinct patterns of association with the three dimensions. Personal devotion was positively associated with years of education, age, and optimism and negatively correlated with neuroticism. Personal conservatism was negatively associated with education, income, age, mastery and positively correlated with neuroticism. Institutional conservatism was negatively correlated with self-esteem and parental education. Covarying for these 14 variables produced little change in their association with psychiatric and substance use outcomes. The impact of the dimensions of religiosity differed as a function of the SLE category. High levels of both personal devotion and institutional conservatism protected against the depressogenic effects of death and personal illness. High levels of personal conservatism were associated with increased sensitivity to relationship problems. These results suggest that the association between religiosity and low risk for symptoms of depression and substance use may be in part causal. The relationship between dimensions of religiosity and response to SLEs is complex but probably of importance in clarifying the nature of the coping process.

Adaptation, Psychological↗
PubMed1998

Twin studies of adult psychiatric and substance dependence disorders: are they biased by differences in the environmental experiences of monozygotic and dizygotic twins in childhood and adolescence?

BACKGROUND: Twin studies have long been used to disentangle the role of genetic and environmental factors in the aetiology of psychiatric disorders. However, the validity of the twin method depends on the equal environment assumption--that monozygotic (MZ) and dizygotic (DZ) twins are equally correlated in their exposure to environmental factors of aetiological importance for the disorder under study. METHODS: Both members of 822 female-female twin pairs from a population-based registry previously assessed for a range of psychiatric and substance use disorders were asked 12 questions assessing the similarity of their environmental experiences in childhood and adolescence. We examined whether the similarity of environmental experiences predicted concordance for psychiatric and substance abuse disorders by both a 'pair-wise' and 'individual' method utilizing logistic regression. We also examined smoking initiation, where prior evidence suggested a role for adolescent social environment. RESULTS: Three factors were derived from these items: 'Childhood treatment', 'Co-socialization' and 'Similitude'. Members of twin pairs agreed substantially in their recollections of these experiences. Compared with DZ twins, MZ twins reported comparable resemblance in their childhood treatment, but socialized together more frequently and reported that parents, teachers and friends more commonly emphasized their similarities. None of these three factors significantly predicted twin resemblance for major depression, generalized anxiety disorder, panic disorder, phobias, nicotine dependence or alcohol dependence. However, co-socialization significantly predicted twin resemblance for smoking initiation and perhaps for bulimia. CONCLUSION: Differential environmental experiences of MZ and DZ twins in childhood and adolescence are unlikely to represent a substantial bias in twin studies of most major psychiatric and substance dependence disorders but may influence twin similarity for the initiation of substance use.

Adolescent↗
PubMed1998

A population-based twin study of self-esteem and gender.

BACKGROUND: Self-esteem (SE), a widely used construct in the social sciences, is usually conceptualized as a reflection of socialization and interpersonal experiences that may differ considerably between the genders. METHODS: The Rosenberg self-esteem scale was assessed at personal interview in both members of 3793 unselected twin pairs (1517 male-male, 856 female-female and 1420 male-female) from the population-based Virginia Twin Registry. Gender effects on SE were assessed by both analysis of variance and biometrical twin modelling. RESULTS: The mean SE score was slightly but significantly lower in women v. men, and in women who grew up with a male v. a female co-twin. Twin modelling suggested that: (i) individual differences in self-esteem in both men and women were best explained by genetic and individual-specific environment factors; (ii) heritability estimates were similar in women (32%) and in men (29%); and (iii) the same genetic factors that influenced SE in women also influenced SE in men. Analyses supported the validity of the equal environment assumption for SE. The heritability of SE cannot be explained by the moderate correlation between SE and symptoms of depression. CONCLUSIONS: These results are inconsistent with prominent gender-related aetiological models for SE, which postulate that individual differences arise from socialization experiences both within and outside the home of origin which differ widely for the two genders. Instead, a significant proportion of the population variance in SE is due to genetically-influenced temperamental variables that are the same in men and women.

Adolescent↗
PubMed1998

Boundaries of major depression: an evaluation of DSM-IV criteria.

OBJECTIVE: Little is known about the boundaries between major depression and milder subsyndromal depressive states. With respect to depressive symptoms, does DSM-IV "carve nature at its joints"? METHOD: In personally interviewed female twins from a population-based registry, the authors examined whether a range of values along three dimensions of the depressive syndrome assessed in the last year (number of symptoms listed in DSM-III-R under diagnostic criterion A for major depressive episode, level of severity or impairment required to score symptoms as present, and duration of episode) predicted future depressive episodes in the index twin and risk of major depression in the co-twin. RESULTS: An increasing number of criterion A symptoms predicted, in a monotonic fashion, a greater risk for future depressive episodes in the index twin as well as a greater risk for major depression in the co-twin. No such consistent relationship was seen with duration of episode. For severity, a single monotonic function predicted risk in the co-twin, while index twins with severe impairment had a substantially higher risk for future episodes than did those with less severe impairment. Four or fewer criterion A symptoms, syndromes composed of symptoms involving no or minimal impairment, and episodes of less than 14 days' duration all significantly predicted both future depressive episodes in the index twin and risk of major depression in the co-twin. CONCLUSIONS: The authors found little empirical support for the DSM-IV requirements for 2 weeks' duration, five symptoms, or clinically significant impairment. Most functions appeared continuous. These results suggest that major depression--as articulated by DSM-IV--may be a diagnostic convention imposed on a continuum of depressive symptoms of varying severity and duration.

Adult↗