Mating system contributes only slightly to female maintenance in gynodioecious Geranium maculatum (Geraniaceae).

Gynodioecy, the co-occurrence of female and hermaphroditic individuals within a population, is an important intermediate in the evolution of separate sexes. The first step, female maintenance, requires females to have higher seed fitness compared with hermaphrodites. A common mechanism thought to increase relative female fitness is inbreeding depression avoidance, the magnitude of which depends on hermaphroditic selfing rates and the strength of inbreeding depression. Less well studied is the effect of biparental inbreeding on female fitness. Biparental inbreeding can affect relative female fitness only if its consequence or frequency differs between sexes, which could occur if sex structure and genetic structure both occur within populations. To determine whether inbreeding avoidance and/or biparental inbreeding can account for female persistence in Geranium maculatum, we measured selfing and biparental inbreeding rates in four populations and the spatial genetic structure in six populations. Selfing rates of hermaphrodites were low and did not differ significantly from zero in any population, leading to females gaining at most a 1-14% increase in seed fitness from inbreeding avoidance. Additionally, although significant spatial genetic structure was found in all populations, biparental inbreeding rates were low and only differed between sexes in one population, thereby having little influence on female fitness. A review of the literature revealed few sexual differences in biparental inbreeding among other gynodioecious species. Our results show that mating system differences may not fully account for female maintenance in this species, suggesting other mechanisms may be involved.

Male-female differences in transitions from first drug opportunity to first use: searching for subgroup variation by age, race, region, and urban status.

Recent studies in the United States suggest that male-female differences in the prevalence of drug use may result from sex differences in opportunities to use drugs rather than from differences in the likelihood of making a transition into drug use once an opportunity has occurred. That is, men have more opportunities to try drugs, but women appear to be just as likely as men to initiate drug use when given the opportunity to do so. This paper examines whether this general observation holds for subgroups defined by age or birth cohort, race/ethnicity, geographic region, and urban status. We analyzed data from the 1991, 1992, and 1993 National Household Surveys on Drug Abuse. We found general consistency across the subgroups studied. Males were more likely than females to have opportunities to use drugs, but the sexes were equally likely to make a transition into drug use once an opportunity had occurred to try a drug. The implications of this evidence are discussed in relation to the epidemiology and prevention of drug use and with respect to future research on sex and gender differences in drug involvement.

"Alcohol dependence" and death: survival analysis of the Baltimore ECA sample from 1981 to 1995.

OBJECTIVE: Evidence is provided about the association between "alcohol-use disorders" and the 14-year risk of death in a community sample. Most prior descriptions of this association come from treatment samples. METHOD: 3,481 adult household residents were recruited into the NIMB Baltimore Epidemiologic Catchment Area survey and interviewed in 1981. The Diagnostic Interview Schedule (DIS) was employed to assess alcohol drinking and other drug-taking behaviors, and to determine fulfillment of DSM-III criteria for "alcohol abuse" and/or "dependence" diagnoses. Participants were followed-up in 1993-1996, by which time 24% of the sample had died. Median age of death was estimated for persons with and without alcohol disorders, and for "heavy" and "nonheavy" drinkers. Cox proportional hazards models adjusted for the influence of age, sex, race, "drug-use disorders," and tobacco smoking. RESULTS: "Alcohol abuse" and/or "dependence" was associated with a higher risk of death and a younger median age of death (adjusted relative risk = 1.3, p = .016). "Heavy" alcohol consumption was also associated with a significantly elevated risk of death. The DIS diagnosis of "alcohol use disorder" helped predict mortality over and above a prediction based solely upon "heavy drinking" (p < .01). CONCLUSIONS: These findings indicate that the observed increased risk of death associated with "alcohol dependence" is not limited to cases severe enough to have been treated but is also present among cases in the household population.

"Drug dependence" and death: survival analysis of the Baltimore ECA sample from 1981 to 1995.

AIMS: Illicit drug use and dependence often are associated with premature death, but available evidence comes mainly from clinical samples. The present paper examines drug-related mortality experience over 14 years in a United States community sample. PARTICIPANTS: Following probability sampling, 3,481 adult community household residents were recruited for the 1981 NIMH Baltimore Epidemiologic Catchment Area survey. Follow-up occurred in 1993-1996. METHODS: Survival analyses were used to estimate median age at death and relative risk of dying in relation to drug use and dependence as assessed in 1981 using the Diagnostic Interview Schedule (DIS). FINDINGS: Cases with DIS "drug dependence" were more likely to have died and to have a younger median age at death (p < .05), with and without statistical adjustment for confounding variables. Higher levels of drug involvement also were associated with increased age-adjusted mortality. CONCLUSIONS: The evidence favors the hypothesis that DIS-elicited "drug dependence," as well as subthreshold drug use, help to account for premature death in this community sample.

First opportunities to try drugs and the transition to first drug use: evidence from a national school survey in Panama.

In recent evidence from the United States, there generally are no male-female differences in the probability of drug use among persons who report an opportunity to try the drugs. This is an important observation that might help us understand male-female differences in later drug use and dependence, but the observation needs to be replicated elsewhere. We begin this replication process using data from a 1996 national school survey of drug involvement among 6,477 students age 12-18 in Panama. We first examine the occurrence of an opportunity to use drugs by grade. We then follow these analyses with an examination of male-female differences in drug opportunity patterns. We found opportunities to use drugs and actual drug use to be greater at higher grade levels. Also, we found the probability of making a transition to use, given an opportunity, to be more likely among upper-grade students. Consistent with results observed in the United States, we found males in Panama to be more likely to have an opportunity to use marijuana, crack-cocaine, and other forms of cocaine, but not more likely than females to make a transition into drug use once an opportunity had occurred to try each drug. These findings are discussed in relation to the epidemiology and prevention of drug use in Panama and elsewhere, and future research on male-female differences in drug involvement.

Comparative epidemiology of initial drug opportunities and transitions to first use: marijuana, cocaine, hallucinogens and heroin.

The earliest stages of involvement with illicit drugs have been understudied. In a recent report, we examined initial opportunities to try marijuana and transitions from first opportunity to first use of that drug. This report extends that work by investigating early involvement with cocaine, heroin, and hallucinogens as well. We examine sex and race ethnicity differences in estimates of having a drug opportunity, and in the probability of progressing from having an opportunity to try a drug to actually using the drug. Self-report interview data collected for the National Household Surveys on Drug Abuse (NHSDA) from 1979 to 1994 were analyzed. Results showed that an estimated 51% of US residents have had an opportunity to try marijuana; comparative estimates for cocaine, hallucinogens, and heroin are 23, 14, and 5%, respectively. Among those who eventually used each drug, the vast majority made the transition from first opportunity to first use within 1 year. Males were more likely than females to have opportunities to try these drugs, but were not more likely than females to progress to actual use once an opportunity occurred. Time trends indicate recent increases from 1990 to 1994 in the estimated probability of using an illicit drug once an opportunity occurs, particularly for hallucinogens. Exploratory analyses on race ethnicity yielded some interesting leads for future research. This study sheds light on the epidemiology of the earliest stages of drug involvement in the USA. Implications for prevention efforts and for our understanding of sex differences in drug involvement are discussed.

Male-female differences in the earliest stages of drug involvement.

AIMS: To examine whether male-female differences in rates of drug use could be traced back to differences in rates of exposure to initial opportunities to try drugs, rather than to sex differences in the probability of making a transition to use, once opportunity has occurred. DESIGN: Cross-sectional sample survey research with nationally representative samples and retrospective assessments. SETTING: United States, 1979-94. PARTICIPANTS: Respondents were 131,226 residents aged 12 years and older, recruited for the National Household Surveys on Drug Abuse by multi-stage probability sampling at nine time points. MEASUREMENTS: Estimated proportion of males and females with an opportunity to use marijuana, cocaine, hallucinogens and heroin; proportions reporting use among those having an opportunity to use each drug; proportion making a "rapid transition" from initial opportunity to initial use. FINDINGS: For each survey year, males were more likely than females to have an initial opportunity to use drugs. However, few male-female differences were observed in the probability of making a transition into drug use, once an opportunity had occurred. CONCLUSIONS: Previously documented male excess in rates of drug use may be due to greater male exposure to opportunities to try drugs, rather than to greater chance of progressing from initial opportunity to actual use. This suggests that sex differences in drug involvement emerge early in the process. Implications of these findings are discussed in relation to the epidemiology and prevention of drug use, and future research on sex differences in drug involvement.

Comparison of the frequency and enjoyability of pleasant events in cocaine abusers vs. non-abusers using a standardized behavioral inventory.

AIMS: To examine whether cocaine abusers differ from non-abusers in their frequency and enjoyability of engaging in various "pleasant events", in order to approximate the density of positive reinforcement experienced in their natural environment. DESIGN: Comparisons of cocaine abusers to normative data and matched controls. SETTING: An outpatient substance abuse treatment center in Burlington, Vermont, USA. PARTICIPANTS: Subjects included 100 individuals enrolled in outpatient treatment for cocaine abuse or dependence and 50 community volunteers without histories of drug abuse or other major psychiatric illness and matched to cocaine-dependent patients on age, sex and SES. MEASUREMENTS: Diagnostic assessments were based upon clinical interviews using the DSM-III-R checklist. The primary focus of this study was the Pleasant Events Schedule (PES), a self-rated behavioral inventory of the frequency and enjoyability of engaging in "pleasant" activities. Cocaine use history, treatment outcome and other relevant variables were also assessed. FINDINGS: Cocaine abusers reliably reported lower frequency of non-social, introverted, passive outdoor and mood-related activities than controls. These differences remained after controlling for demographic and life-style differences between groups, with the exception of mood-related activities. Perceived enjoyability of the activities did not differ across groups. Intravenous cocaine use and prior treatment for cocaine abuse predicted particularly low frequency of pleasant activities. Greater frequency of non-social activities predicted better treatment outcome. CONCLUSIONS: Drug abuse is associated with low density of certain types of non-drug reinforcement. Systematic increases in these activities may improve treatment outcome.

Initial opportunity to use marijuana and the transition to first use: United States, 1979-1994.

A renewed American interest in marijuana has coincided with our research group's focus on the earliest stages of drug involvement. Here, we have studied the transition from an initial opportunity to try marijuana to the subsequent use of this drug. We analyzed self-report interview data gathered from nationally representative samples of the United States National Household Surveys on Drug Abuse, 1979-1994. The evidence indicates that the estimated prevalence of an opportunity to try marijuana has been rather stable for 15 years. However, there are recent increases in the probability of rapidly progressing from first marijuana opportunity to first marijuana use, among persons given an opportunity to use. In addition, the transition from first marijuana opportunity to eventual marijuana use seems to depend upon age at first opportunity. This epidemiological evidence on the transition from marijuana opportunity to marijuana use, the first to be published based on a nationally representative US sample, highlights directions for future research and a focus for prevention efforts.

Effects of response cost and unit dose on alcohol self-administration in moderate drinkers.

Alcohol self-administration by nonhumans and alcoholic humans decreases as the response requirement to obtain the drug increases. Also, increases in dose or concentration of alcohol, increase consumption up to a maximum in these populations, after which further increases in dose decrease intake. In the present study, the effects of response cost and dose on alcohol self-administration were investigated in moderate drinkers (12-45 drinks/week). Three male volunteers self-administered alcohol (commercial beer) during 2h sessions twice weekly. Alcohol was available under a fixed-ratio (FR) schedule of reinforcement. Response requirement (FR100-1600) and dose (2 and 4oz of beer) were varied separately across sessions using a within-subjects design. As response cost increased, consumption and overall rates of responding generally changed in an inverted U-shaped manner. Maximal consumption was observed at the 4oz dose. These orderly relations between response cost, dose and alcohol self-administration extend prior findings in nonhumans and alcoholics to moderate drinkers. Such consistencies support a position that a common set of variables control alcohol self-administration across these populations.

Covariation of alpha 2-adrenoceptor density and function following irreversible antagonism with EEDQ.

1. Administration of the irreversible antagonist, N-ethoxycarbonyl-2-ethoxy-1,2-dihydroquinoline, (EEDQ, 2 mg kg-1, i.p.) to mice reduced binding of [3H]-RX 821002 (2-methoxy-idazoxan) to alpha 2-adrenoceptors in whole mouse brain by 75% 24 h later. The receptor binding returned over time only being reduced by 25% by 16 days post administration; the time taken for binding to return to 50% of control levels was estimated to be 5.25 days. 2. EEDQ administration also resulted in the loss of the sedative effect of the alpha 2-adrenoceptor agonist, medetomidine, measured by the holeboard test of directed exploration and locomotor activity. Agonist-induced sedation returned to control values by 8 days post EEDQ administration. 3. EEDQ administration also resulted in the loss of the hypothermic response to medetomidine (0.1 mg kg-1, i.p.). Medetomidine-induced hypothermia returned to control values by 12 days post EEDQ administration. 4. Pretreatment with the selective alpha 2-adrenoceptor antagonist, RX 821002 (0.1-3.0 mg kg-1, i.p.) 45 min before EEDQ prevented the loss of alpha 2-adrenoceptors as well as the blockade of medetomide-induced sedation and hypothermia by EEDQ. 5. The results of these experiments indicate that there is significant receptor reserve for alpha 2-adrenoceptor-mediated behavioural and physiological responses.