A Contagion Model for Within-Family Transmission of Drug Abuse

The dynamics of heroin and illicit opioid use disorder, casual use, treatment, and recovery: A mathematical modeling analysis

A leading crisis in the United States is the opioid use disorder (OUD) epidemic. Opioid overdose deaths have been increasing, with over 100,000 deaths due to overdose from April 2020 to April 2021. This paper presents a mathematical model to address illicit OUD (IOUD), initiation, casual use, treatment, relapse, recovery, and opioid overdose deaths within an epidemiological framework. Within this model, individuals remain in the recovery class unless they relapse back to use and due to the limited availability of specialty treatment facilities for individuals with OUD, a saturation treatment function was incorporated. Additionally, a casual user class and its corresponding specialty treatment class were incorporated. We use both heroin and all-illicit opioids datasets to find parameter estimates for our models. Bistability of equilibrium solutions was found for realistic parameter values for the heroin-only dataset. This result implies that it would be beneficial to increase the availability of treatment. An alarming effect was discovered about the high overdose death rate: by 2046, the disorder-free equilibrium would be the only stable equilibrium. This consequence is concerning because it means the epidemic would end due to high overdose death rates. The IOUD model with a casual user class, its sensitivity results, and the comparison of parameters for both datasets, showed the importance of not overlooking the influence that casual users have in driving the all-illicit opioid epidemic. Casual users stay in the casual user class longer and are not going to treatment as quickly as the users of the heroin epidemic. Another result was that the users of the all-illicit opioids were going to the recovered class by means other than specialty treatment. However, the change in the relapse rate has more of an influence for those individuals than in the heroin-only epidemic. The results above from analyzing this model may inform health and policy officials, leading to more effective treatment options and prevention efforts.

Contagious Transmission in a Swedish National Sample of Alcohol Use Disorders as a Function of Geographical Proximity Among Siblings and Propinquity-of-Rearing Defined Acquaintances

OBJECTIVE

The purpose of this study was to determine whether alcohol use disorder (AUD) can be transmitted contagiously in siblings and likely acquaintances growing up close to one another (Propinquity-of-Rearing Defined Acquaintances [PRDAs]).

METHOD

PRDAs were pairs of same-age subjects growing up within 1 km of each other and sharing the same school class, where one of whom (PRDA1) was first registered for AUD at age 15 or older. Using adult residential location, we predicted proximity-dependent risk for an AUD first registration in a second PRDA within 3 years of PRDA1's registration.

RESULTS

In 150,195 informative siblings, cohabitation status (hazard ratio [HR] = 1.22, 95% confidence interval [CI] [1.08, 1.37]), but not proximity, predicted risk for AUD onset. In 114,375 informative PRDA pairs, a log model fit best, predicting lower risk the greater the distance (HR = 0.88, 95% CI [0.84, 0.92]) with risks for AUD at 10, 50, and 100 km from affected PRDA1 cases equaling, respectively: 0.73 [0.66, 0.82], 0.60 [0.51, 0.72], and 0.55 [0.45, 0.68]. Within PRDA acquaintanceships, results resembled those found among PRDA pairs. The proximity-dependent contagious risk for AUD among PRDA pairs was attenuated by increasing age, lower genetic risk, and higher educational attainment.

CONCLUSIONS

Cohabitation but not distance predicted transmission of AUD between siblings. However, contagious transmission of AUD among acquaintances growing up and attending school together was present and attenuated by increasing distance in adulthood. The impact of adult proximity on transmission was moderated by age, educational attainment, and genetic risk for AUD. Our results provide support for the validity of contagion models for AUD.

The Impact of Parental Opioid Use Disorder on Children in Rural Texas

The impact of opioid use disorder (OUD) on children is of increasing concern to providers and communities and is yet to be fully understood. Children and families in rural areas are particularly vulnerable due to decreased access to care, lower socioeconomic status, and lower rates of health insurance coverage. This qualitative secondary data analysis of transcripts from interviews with community stakeholders specifically examined responses when asked how parental OUD impacted children in their rural communities. Methods and Materials: As part of a larger community assessment, 11 focus group and three individual interviews with a variety of stakeholders most likely to encounter those with or at risk for substance use disorder from a predominately rural region of Texas were held in October of 2019. During one-hour sessions a scripted interview guide was used to ask open-ended questions to identify the prevalence and impact of OUD within the community. Transcripts of recorded interviews were coded by three researchers using conventional content analysis focusing on discussion of how parental OUD impacted children in their rural communities. Codes were classified into themes based on consensus. Results: Identified themes were (1) Community Concern for Families; (2) Impaired Parents, Neglected Children, and (3) Intergenerational Normalization of Substance Misuse. Conclusions: The impact of parental OUD and SUD was a concern for participants. Findings have implications for strategies to prevent and mitigate adverse outcomes for children and families in rural areas.

Parental characteristics and offspring mental health and related outcomes: a systematic review of genetically informative literature

Various parental characteristics, including psychiatric disorders and parenting behaviours, are associated with offspring mental health and related outcomes in observational studies. The application of genetically informative designs is crucial to disentangle the role of genetic and environmental factors (as well as gene-environment correlation) underlying these observations, as parents provide not only the rearing environment but also transmit 50% of their genes to their offspring. This article first provides an overview of behavioural genetics, matched-pair, and molecular genetics designs that can be applied to investigate parent-offspring associations, whilst modelling or accounting for genetic effects. We then present a systematic literature review of genetically informative studies investigating associations between parental characteristics and offspring mental health and related outcomes, published since 2014. The reviewed studies provide reliable evidence of genetic transmission of depression, criminal behaviour, educational attainment, and substance use. These results highlight that studies that do not use genetically informative designs are likely to misinterpret the mechanisms underlying these parent-offspring associations. After accounting for genetic effects, several parental characteristics, including parental psychiatric traits and parenting behaviours, were associated with offspring internalising problems, externalising problems, educational attainment, substance use, and personality through environmental pathways. Overall, genetically informative designs to study intergenerational transmission prove valuable for the understanding of individual differences in offspring mental health and related outcomes, and mechanisms of transmission within families.

Association of Opioid Prescription Initiation During Adolescence and Young Adulthood With Subsequent Substance-Related Morbidity

IMPORTANCE

Concerns about adverse outcomes associated with opioid analgesic prescription have led to major guideline and policy changes. Substantial uncertainty remains, however, regarding the association between opioid prescription initiation and increased risk of subsequent substance-related morbidity.

OBJECTIVE

To examine the association of opioid initiation among adolescents and young adults with subsequent broadly defined substance-related morbidity.

DESIGN, SETTING, AND PARTICIPANTS

This cohort study analyzed population-register data from January 1, 2007, to December 31, 2013, on Swedish individuals aged 13 to 29 years by January 1, 2013, who were naive to opioid prescription. To account for confounding, the analysis compared opioid prescription recipients with recipients of nonsteroidal anti-inflammatory drugs as an active comparator, compared opioid-recipient twins and other multiple birth individuals with their nonrecipient co-multiple birth offspring (co-twin control), examined dental prescription as a specific indication, and included individual, parental, and socioeconomic covariates. Data were analyzed from March 30, 2019, to January 22, 2020.

EXPOSURES

Opioid prescription initiation, defined as first dispensed opioid analgesic prescription.

MAIN OUTCOMES AND MEASURES

Substance-related morbidity, assessed as clinically diagnosed substance use disorder or overdose identified from inpatient or outpatient specialist records, substance use disorder or overdose cause of death, dispensed pharmacotherapy for alcohol use disorder, or conviction for substance-related crime.

RESULTS

Among the included cohort (n = 1 541 862; 793 933 male [51.5%]), 193 922 individuals initiated opioid therapy by December 31, 2013 (median age at initiation, 20.9 years [interquartile range, 18.2-23.6 years]). The active comparator design included 77 143 opioid recipients without preexisting substance-related morbidity and 229 461 nonsteroidal anti-inflammatory drug recipients. The adjusted cumulative incidence of substance-related morbidity within 5 years was 6.2% (95% CI, 5.9%-6.5%) for opioid recipients and 4.9% (95% CI, 4.8%-5.1%) for nonsteroidal anti-inflammatory drug recipients (hazard ratio, 1.29; 95% CI, 1.23-1.35). The co-twin control design produced comparable results (3013 opioid recipients and 3107 nonrecipients; adjusted hazard ratio, 1.43; 95% CI, 1.02-2.01), as did restriction to analgesics prescribed for dental indications and additional sensitivity analyses.

CONCLUSIONS AND RELEVANCE

Among adolescents and young adults analyzed in this study, initial opioid prescription receipt was associated with an approximately 30% to 40% relative increase in risk of subsequent substance-related morbidity in multiple designs that adjusted for confounding. These findings suggest that this increase may be smaller than previously estimated in some other studies.

Within-Family Transmission of Alcohol Use Disorder in Parent-Offspring, Sibling, and Cousin Pairs: A Contagion Model

To determine whether alcohol use disorder (AUD) is transmitted within families as predicted by contagion, we examined parent-offspring, siblings, and cousin pairs ascertained from Swedish registries with a primary case with AUD. Our outcome variable was AUD registration in at-risk secondary cases. In offspring, risks for AUD registration in the 3 years after a parental index registration residing in the same household, neighborhood, or municipality increased by 1.6%, -0.5%, and 0.3%, respectively. For siblings of sibling index cases, parallel results were 3.2%, 1.2%, and 0.3%. For cousins of cousin index cases, no excess risk was seen for those residing in the same neighborhood or municipality. In siblings, AUD transmission was stronger in same versus opposite sex pairs and from older to younger versus younger to older siblings. These results support the hypothesis that AUD is transmitted among close family relationships and over limited geographical distances by a temporally dynamic contagion model.

Facilitating Versus Inhibiting the Transmission of Drug Abuse from High-Risk Parents to Their Children: A Swedish National Study

We seek to identify factors that facilitate or inhibit transmission of drug abuse (DA) from high-risk parents to their children. In 44,250 offspring of these parents, ascertained from a Swedish national sample for having a mother and/or father with DA, we explored, using Cox models, how the prevalence of DA was predicted by potentially malleable risk factors in these high-risk parents, their spouses and the rearing environment they provided. Analyses of offspring of discordant high-risk siblings and offspring of discordant sibling-in-laws and step-parents aided causal inference. Risk for DA in the children was associated with high-risk and married-in parental externalizing psychopathology, a range of other features of these parents (e.g., low education and receipt of welfare), and aspects of the rearing environment (e.g., neighborhood deprivation and number of nearby drug dealers). Offspring of discordant high-risk siblings, siblings-in-laws and step-parents suggested that nearly all these associations were partly causal. A multivariate analysis utilizing offspring of discordant high-risk siblings identified the six most significant potentially malleable risk factors for offspring DA: (1) criminal behavior (CB) in married-in parent, (2) community peer deviance, (3) broken family, (4) DA in high-risk parent, (5) CB in high-risk parent and (6) number of family moves. Children in the lowest decile of risk had a 50% reduction in their DA prevalence, similar to that seen in the general population. We conclude that transmission of DA from high-risk parents to children partly results from a range of potentially malleable risk factors that could serve as foci for intervention.

Immigrant enclaves and risk of drug involvement among asylum-seeking immigrants in Sweden: A quasi-experimental study

BACKGROUND

Sweden is a major host nation for asylum-seeking immigrants, and residential placement of these immigrants is an important policy concern. This quasi-experimental study estimated of the impact of being placed into an "immigrant enclave" on risk of officially-recognized drug involvement (ORDI) among asylum-seeking immigrants over a 15-year period.

METHODS

All data come from Swedish registries. The sample consisted of (a) asylum-seeking immigrants aged 5-35 years old at arrival (N = 51,017) that were subject to a nationwide policy (enforced 1987-1991) that dispersed asylum-seeking immigrants across municipalities, and (b) native-born Swedes aged 15 and older during this same period (N = 1,040,311). Neighborhood immigrant composition was quantified using the Reardon Index; residents of "immigrant enclave" neighborhoods (n = 960) were compared to residents of all other neighborhoods (n = 2,471). Cox proportional hazards models assessed the relationship between living in an enclave and risk of ORDI, identified by national registries, through 2015.

RESULTS

Overall, 29.7% of immigrants were assigned to, and 25.5% of Swedes lived in, an enclave. Cumulative incidence of ORDI in enclaves was 6.34% as compared to 6.89% in other neighborhoods. Immigrants living in an enclave had lower risk of ORDI (Hazard ratio (HR): 0.86, 95% Confidence Interval (CI): 0.77 - 0.96). This protective association was marginally stronger in lower poverty areas. Native-born Swedes living in an enclave had higher risk of ORDI (HR: 1.05, 95% CI: 1.03-1.08), a relationship that was exacerbated by neighborhood poverty.

CONCLUSIONS

Neighborhood immigrant composition is associated with risk of ORDI, with differential associations for immigrants and native-born populations.

Associations of Parental Marijuana Use With Offspring Marijuana, Tobacco, and Alcohol Use and Opioid Misuse

IMPORTANCE

Marijuana use is increasing among adults and often co-occurs with other substance use; therefore, it is important to examine whether parental marijuana use is associated with elevated risk of substance use among offspring living in the same household.

OBJECTIVE

To examine associations of parental marijuana use with offspring marijuana, tobacco, and alcohol use and opioid misuse.

DESIGN, SETTING, AND PARTICIPANTS

This cross-sectional study used survey data from the 2015 through 2018 National Surveys on Drug Use and Health (NSDUH), which provide nationally representative data on adolescents or young adults living with a parent (the mother or the father). Annual average percentages were based on survey sampling weights. Final analyses were conducted September 21 through 23, 2019.

EXPOSURES

Parental marijuana use status.

MAIN OUTCOMES AND MEASURES

Offspring self-reported use of marijuana, tobacco, or alcohol or misuse of opioids.

RESULTS

Survey respondents included 24 900 father-offspring or mother-offspring dyads sampled from the same household. Among mothers living with adolescent offspring, 8.2% (95% CI, 7.3%-9.2%) had past-year marijuana use, while 7.6% (95% CI, 6.2%-9.2%) of mothers living with young adult offspring had past-year marijuana use. Among fathers living with adolescent offspring, 9.6% (95% CI, 8.5%-10.8%) had past-year marijuana use, and 9.0% (95% CI, 7.4%-10.9%) of fathers living with young adult offspring had past-year marijuana use. Compared with adolescents whose mothers never used marijuana, adjusted relative risk (ARR) of past-year marijuana use was higher among those whose mothers had lifetime (without past-year) marijuana use (ARR, 1.3; 95% CI, 1.1-1.6; P = .007), less than 52 days of past-year marijuana use (ARR, 1.7; 95% CI, 1.1-2.7; P = .02), or 52 days or more of past-year marijuana use (ARR, 1.5; 95% CI, 1.1-2.2; P = .02). Compared with young adults whose mothers never used marijuana, adjusted risk of past-year marijuana use was higher among those whose mothers had lifetime (without past-year) marijuana use (ARR, 1.4; 95% CI, 1.1-1.7; P = .001), less than 52 days of past-year marijuana use (ARR, 1.5; 95% CI, 1.0-2.3; P = .049), or 52 days or more of past-year marijuana use (ARR, 1.8; 95% CI, 1.3-2.5; P = .002). Compared with adolescents whose fathers never used marijuana, adolescents whose fathers had less than 52 days of past-year marijuana use were more likely to use marijuana (ARR, 1.8; 95% CI, 1.2-2.7; P = .006). Compared with young adults whose fathers never used marijuana, young adults whose fathers had 52 days or more of past-year marijuana use were more likely to use marijuana (ARR, 2.1; 95% CI, 1.6-2.9; P < .001). Compared with their peers whose parents never used marijuana and after adjusting for covariates, the adjusted risk of past-year tobacco use was higher among adolescents whose mothers had lifetime marijuana use (ARR, 1.3; 95% CI, 1.0-1.6; P = .03), less than 52 days of past-year marijuana use (ARR, 1.5; 95% CI, 1.0-2.1; P = .04), or 52 days or more of past-year marijuana use (ARR, 1.6; 95% CI, 1.1-2.3; P = .03); adolescents whose fathers had lifetime marijuana use (ARR, 1.5; 95% CI, 1.1-1.9; P = .004) or 52 days or more of past-year marijuana use (ARR, 1.8; 95% CI, 1.2-2.7; P = .006); young adults whose mothers had lifetime marijuana use (ARR, 1.2; 95% CI, 1.0-1.4; P = .04); and young adults whose fathers had 52 days or more of past-year marijuana use (ARR, 1.4; 95% CI, 1.0-1.9; P = .046). Compared with their peers whose parents had no past marijuana use and after adjusting for covariates, risk of past-year alcohol use was higher among adolescents whose mothers had lifetime marijuana use (ARR, 1.2; 95% CI, 1.1-1.4; P = .004), less than 52 days of past-year marijuana use (ARR, 1.5; 95% CI, 1.2-1.9; P = .002), or 52 days or more of past-year marijuana use (ARR, 1.3; 95% CI, 1.0-1.7; P = .04). After adjusting for covariates, parental marijuana use was not associated with opioid misuse by offspring.

CONCLUSIONS AND RELEVANCE

In this cross-sectional study, parental marijuana use was associated with increased risk of substance use among adolescent and young adult offspring living in the same household. Screening household members for substance use and counseling parents on risks posed by current and past marijuana use are warranted.

Geographical proximity and the transmission of drug abuse among siblings: evaluating a contagion model in a Swedish National Sample

AIMS

Can drug abuse (DA) be transmitted psychologically between adult siblings consistent with a social contagion model?

METHODS

We followed Swedish sibling pairs born in 1932-1990 until one of them, sibling1 (S1), had a first DA registration. We then examined, using Cox regression, the hazard rate for a first registration for DA in sibling2 (S2) within 3 years of a first DA registration in S1 as a function of their geographical proximity. We examined 153 294 informative pairs. To control for familial confounding, we repeated these analyses in sibships containing multiple pairs, comparing risk in different siblings with their proximity to S1. DA was recorded in medical, criminal or pharmacy registries.

RESULTS

The best-fit model predicted risk for DA in S2 as a function of the log of kilometres between S1 and S2 with parameter estimates (±95% confidence intervals) of 0.94 (0.92; 0.95). Prediction of DA included effects of cohabitation and an interaction of proximity and time since S1 registration with stronger effects of proximity early in the follow-up period. Proximity effects were stronger for smaller S1-S2 age differences and for same- v. opposite-sex pairs. Sibship analyses confirmed sibling-pair results.

CONCLUSIONS

Consistent with a social contagion model, the probability of transmission of a first registration for DA in sibling pairs is related to their geographical proximity and similarity in age and sex. Such effects for DA are time-dependent and include cohabitation effects. These results illustrate the complexity of the familial aggregation of DA and support efforts to reduce their contagious spread within families in adulthood.

Contagion models for the transmission of drug abuse among propinquity-of-rearing defined acquaintances: A Swedish national study

BACKGROUND

Can we validate a contagion model for drug abuse (DA) in Propinquity-of-Rearing Defined Acquaintances (PRDAs)?

METHODS

PRDAs were defined as pairs of same-age males born 1975-1990 who grew up within 2 km of each other, one of whom (PRDA1) being first registered for DA in national registries. Using adult residential location, we predicted, using regression splines, proximity-dependent risk for DA first registration in a second PRDA (PRDA2) within 3 years of PRDA1's registration.

RESULTS

In 181,743 PRDA pairs, the best-fit model, controlling for age and PRDA2 community risk, included 2 slopes of proximity-risk relationships in childhood and three in adulthood. Risk for DA in PRDA2 was strongly predicted by childhood proximity to PRDA1: 0 to 0.5 km - Hazard ratio (HR) per kilometer 0.52 and 0.6-2 km 0.78. HRs for PRDA2 as a function of adult proximity to PRDA1 were: 0-1 km 0.887, 1-75 km 0.996 and >75 km 0.9997. Proximity-dependent PRDA2 risk was moderated by age, familial risk and educational attainment, attenuated by increasing PRDA1-PRDA2 age differences and stronger for older to younger versus younger to older pairs.

CONCLUSIONS

Transmission of DA risk between acquaintances growing up together was attenuated by increasing distance in adulthood. Strength of the acquaintance, indexed by childhood propinquity and age difference, modified transmission strength. The impact of adult proximity on transmission was reduced in acquaintances with higher resistance to DA due to older age, higher educational attainment or lower familial risk. Our results support the validity of DA contagion models.

Geographic proximity is associated with transmission of suicidal behaviour among siblings

OBJECTIVE

The aim of this study was to clarify the role of 'contagion', or social transmission, in risk of suicidal behaviour (SB) among siblings.

METHODS

We followed Swedish sibling pairs until one of them (S1; N = 111,848) was registered for a suicide attempt or completion. We tested the effect of geographic proximity between siblings on risk of a first SB registration of S1's sibling (S2). To control for familial confounding, we conducted complementary analyses of sibling trios (N = 701), comparing risk in different siblings as a function of their respective proximity to S1.

RESULTS

The best-fitting model across sibling pairs included an effect of distance between siblings (HR = 0.96, 95% CI = 0.93-0.99). Hazard ratios declined quickly up to 25 km and largely stabilized beyond 150 km. Across all pairs, a larger age difference between siblings was associated with reduced SB risk (HR = 0.96 95% CI = 0.93-0.98). Findings were consistent within the sibling trios.

CONCLUSIONS

Consistent with the concept of suicide contagion, risk of suicidal behaviour subsequent to a sibling's suicide completion or attempt is higher as a function of sibling closeness. These findings are robust to potentially confounding familial factors.

The Nature of the Shared Environment

While a standard part of twin modeling, the magnitude of shared environment (c2) is rarely examined by comparing estimates obtained using other methods. To clarify these effects on familial resemblance, we estimated c2 for 20 diverse phenotypes in: (i) monozygotic and dizygotic twins, (ii) all step-siblings, and (iii) reared together and apart half-siblings, ascertained from the Swedish general population. The mean c2 estimates (± 95% CIs) differed across methods and were higher from twins (0.18; 0.13-0.23) than from the step (0.12; 0.09-0.14) and half-sibs (0.09; 0.06-0.13). c2 estimates correlated moderately across these three methods (ICC = + 0.28). When step-siblings from blended (each sib biologically related to one parent) and adoption-like families (one sib offspring of both parents and one of neither), were examined separately, resemblance was much lower in the latter. We need to clarify the range of environmental processes now considered together under the term "shared environment."