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Biomedical subjects

Robert D Gibbons

Publications and source records attributed to Robert D Gibbons.

8 recordsLinked to original sources
PubMed2006

Rater bias in a blinded randomized placebo-controlled psychiatry trial.

Rater bias occurs when rater knowledge of treatment assignment modifies the outcome assessment. Raters may be unconsciously influenced by inclinations for or against a particular treatment and consequently may give a more or less generous assessment depending upon these biases. Blinding of raters by keeping raters unaware of treatment assignment is one way to limit bias influencing assessment due to knowledge of treatment assignment. Unblinding may be particularly problematic in efficacy studies comparing placebo to drugs and/or non-drug psychotherapy treatments where subjects may reveal drug side-effects or mention their therapist by name, thus unblinding their treatment assignment. We present a new instrumental variable statistical approach for assessing the association between success in blinding and its impact on efficacy estimates of active drug and/or cognitive behavioural psychotherapy versus placebo in the multicentre comparative treatment study of panic disorder. Despite the uncertainty involved in assessing bias that may be unobserved and unconscious, we will show how to derive a bound for the impact of rater bias.

Bias↗
PubMed2006

The relationship between antidepressant prescription rates and rate of early adolescent suicide.

OBJECTIVE: In 2002, 264 children and adolescents ages 5-14 died by suicide in the United States, the fifth leading cause of death. Of these suicides, 260 were in the 10-14 year age group, making suicide the third largest cause of death behind accidents and malignancy. Although 60% of suicides in the general population occur in the midst of a mood disorder, usually untreated, little is known about the relationship between treatment of mood disorders and youth suicide. The FDA recently linked adverse event reports of suicidal ideation among children and adolescents in randomized controlled trials to selective serotonin reuptake inhibitors (SSRIs) and consequently required a change in labeling that included a black box warning regarding SSRI use for all age groups. Given that the age-adjusted suicide rate is about six times higher in 15-19 year olds compared with 10-14 year olds, the risk-benefit ratio may be different in younger children. Therefore, this study examined the association between antidepressant medication prescription rate and suicide rate in children ages 5-14 prior to the FDA findings by analyzing associations at the county level across the United States. METHOD: National county-level suicide rate data among children ages 5-14 were broken down by sex, income, and race during the period 1996-1998. National county-level antidepressant prescription rate data were expressed as number of pills prescribed per person. The primary outcome measure was the suicide rate in each county expressed as number of suicides for a given population size. RESULTS: After adjustment for sex, race, income, access to mental health care, and county-to-county variability in suicide rates, higher SSRI prescription rates were associated with lower suicide rates in children and adolescents. CONCLUSIONS: The aggregate nature of these observational data precludes a direct causal interpretation of the results. More SSRI prescriptions are associated with lower suicide rates in children and may reflect antidepressant efficacy, treatment compliance, better quality mental health care, and low toxicity in the event of a suicide attempt by overdose.

Adolescent↗
PubMed2005

The relationship between antidepressant medication use and rate of suicide.

BACKGROUND: Approximately 30 000 people die annually by suicide in the United States. Although 60% of suicides occur during a mood disorder, mostly untreated, little is known about the relationship between antidepressant medication use and the rate of suicide in the United States. OBJECTIVE: To examine the association between antidepressant medication prescription and suicide rate by analyzing associations at the county level across the United States. DESIGN: Analysis of National Vital Statistics from the Centers for Disease Control and Prevention. SETTING: All US counties. PARTICIPANTS: All US individuals who committed suicide between 1996 and 1998. MAIN OUTCOME MEASURES: National county-level suicide rate data are broken down by age, sex, income, and race for the period of 1996 to 1998. National county-level antidepressant prescription data are expressed as number of pills prescribed. The primary outcome measure is the suicide rate in each county expressed as the number of suicides for a given population size. RESULTS: The overall relationship between antidepressant medication prescription and suicide rate was not significant. Within individual classes of antidepressants, prescriptions for selective serotonin reuptake inhibitors (SSRIs) and other new-generation non-SSRI antidepressants (eg, nefazodone hydrochloride, mirtazapine, bupropion hydrochloride, and venlafaxine hydrochloride) are associated with lower suicide rates (both within and between counties). A positive association between tricyclic antidepressant (TCA) prescription and suicide rate was observed. Results are adjusted for age, sex, race, income, and county-to-county variability in suicide rates. Higher suicide rates in rural areas are associated with fewer antidepressant prescriptions, lower income, and relatively more prescriptions for TCAs. CONCLUSIONS: The aggregate nature of these observational data preclude a direct causal interpretation of the results. A high number of TCA prescriptions may be a marker for those counties with more limited access to quality mental health care and inadequate treatment and detection of depression, which in turn lead to increased suicide rates. By contrast, increases in prescriptions for SSRIs and other new-generation non-SSRIs are associated with lower suicide rates both between and within counties over time and may reflect antidepressant efficacy, compliance, a better quality of mental health care, and low toxicity in the event of a suicide attempt by overdose.

Adolescent↗
PubMed2004

Contextual predictors of mental health service use among children open to child welfare.

BACKGROUND: Children involved with child welfare systems are at high risk for emotional and behavioral problems. Many children with identified mental health problems do not receive care, especially ethnic/minority children. OBJECTIVE: To examine how patterns of specialty mental health service use among children involved with child welfare vary as a function of the degree of coordination between local child welfare and mental health agencies. DESIGN: Specialty mental health service use for 1 year after contact with child welfare was examined in a nationally representative cohort of children aged 2 to 14 years. Predictors of service use were modeled at the child/family and agency/county levels. Child- and agency-level data were collected between October 15, 1999, and April 30, 2001. SETTING: Ninety-seven US counties. PARTICIPANTS: A total of 2823 child welfare cases (multiple informants) from the National Survey of Child and Adolescent Well-being and agency-level key informants from the participating counties. MAIN OUTCOME MEASURES: Specialty mental health service use during the year after contact with the child welfare system. RESULTS: Only 28.3% of children received specialty mental health services during the year, although 42.4% had clinical-level Child Behavior Checklist scores. Out-of-home placement, age, and race/ethnicity were strong predictors of service use rates, even after controlling for Child Behavior Checklist scores. Increased coordination between local child welfare and mental health agencies was associated with stronger relationships between Child Behavior Checklist scores and service use and decreased differences in rates of service use between white and African American children. CONCLUSIONS: Younger children and those remaining in their homes could benefit from increased specialty mental health services. They have disproportionately low rates of service use, despite high levels of need. Increases in interagency coordination may lead to more efficient allocation of service resources to children with the greatest need and to decreased racial/ethnic disparities.

Affective Symptoms↗
PubMed2004

Estimation and classification of fMRI hemodynamic response patterns.

In this paper, we propose an approach to modeling functional magnetic resonance imaging (fMRI) data that combines hierarchical polynomial models, Bayes estimation, and clustering. A cubic polynomial is used to fit the voxel time courses of event-related design experiments. The coefficients of the polynomials are estimated by Bayes estimation, in a two-level hierarchical model, which allows us to borrow strength from all voxels. The voxel-specific Bayes polynomial coefficients are then transformed to the times and magnitudes of the minimum and maximum points on the hemodynamic response curve, which are in turn used to classify the voxels as being activated or not. The procedure is demonstrated on real data from an event-related design experiment of visually guided saccades and shown to be an effective alternative to existing methods.

Bayes Theorem↗
PubMed2003

Waiting for organ transplantation: results of an analysis by an Institute of Medicine Committee.

One of the most visible and contentious issues regarding the fairness of the original system of organ procurement and allocation is the argument that it resulted in great disparities in the total amount of time a patient waited for an organ (i.e. the time from registration at a transplantation center to transplant), depending on where he or she lived. In an attempt to resolve this debate, Congress charged the National Academy of Sciences, Institute of Medicine to perform an independent study of the original system and proposed rule changes. In an analysis of approximately 68,000 transplant waiting list records, the committee developed several conclusions and recommendations largely specific to liver transplantation policies. The purpose of this paper is to describe both the results of the study and the statistical foundations of the mixed-effects multinomial logistic regression model that led to the committee's conclusions.

Adolescent↗
PubMed2002

A study to determine the nitroglycerin ointment dose and dosing interval that best promote the healing of chronic anal fissures.

PURPOSE: The aim of this study was to determine the optimal dose and dosing interval of nitroglycerin ointment to heal chronic anal fissures. METHOD: A randomized, double-blind study of intra-anally applied nitroglycerin ointment (Anogesic) was conducted in 17 centers in 304 patients with chronic anal fissures. The patients were randomly assigned to one of eight treatment regimens (0.0, 0.1, 0.2, 0.4 percent nitroglycerin ointment applied twice or three times per day), for up to eight weeks. A dose-measuring device standardized the delivery of 374 mg ointment. Healing of fissures (complete reepithelialization) was assessed by physical examination using an observer unaware of treatment allocation. The subjects assessed pain intensity daily by completing a diary containing a visual analog scale for average pain intensity for the day, the worst pain intensity for the day, and pain intensity at the last defecation. RESULTS: There were no significant differences in fissure healing among any of the treatment groups; all groups, including placebo had a healing rate of approximately 50 percent. This rate of placebo response was inexplicably higher than previously reported in the literature. Treatment with 0.4 percent (1.5 mg) nitroglycerin ointment was associated with a significant (P < 0.0002) decrease in average pain intensity compared with vehicle as assessed by patients with a visual analog scale. The decreases were observed by Day 4 of treatment. At 8 weeks the magnitude of the difference between 0.4 percent nitroglycerin and control was a 21 percent reduction in average pain. Treatment was well tolerated, with only 3.29 percent of patients discontinuing treatment because of headache. Headaches were the primary adverse event and were dose related. CONCLUSION: Nitroglycerin ointment did not alter healing but significantly and rapidly reduced the pain associated with chronic anal fissures.

Adult↗