Introduction
Peer influence is a key factor that shapes youth’s decisions and actions around substance use, sexual activity, and outcomes such as teen pregnancy. Peer influence can occur through digital communication (e.g., texting), social media or other digital spaces, or in person. Youth-supporting professionals should understand the different ways youth communicate with their peers and help youth navigate peer influence across in-person and online interactions. Because peers can influence youth in different ways, youth-supporting professionals should have the knowledge to encourage positive peer relationships and informed decision-making related to substance use and sexual activity.
Although teen pregnancy in the United States has declined over time,1 certain groups of youth continue to experience higher rates of pregnancy relative to the general population, including youth experiencing the child welfare or juvenile justice systems, or youth experiencing homelessness.2,3,4 Similarly, substance use rates are high among these same populations.5,6,7,8,9,10,11 The high rates of substance use and teen pregnancy suggest the importance of prevention strategies that address the broader contexts shaping youth decisions. While many factors shape these decisions, peer influence is particularly important because it both increases risk and protects against substance use and risky sexual activity.12,13 Peer norms, social acceptance, and social pressure can encourage substance use and sexual activity, but peers can also reinforce safer choices and provide positive support. For this reason, this research synthesis focuses on peer influence as a key and modifiable point of prevention. Targeting peer dynamics—for example, by correcting misperceived norms, strengthening prosocial peer networks, and building skills to resist negative peer pressure—can offer an opportunity to reduce substance use and related sexual behaviors, ultimately reducing the risk of unintended teen pregnancy.
In this summary, the term “risky sexual activity” refers to consensual sexual activity that increases the likelihood of unintended teen pregnancy or sexually transmitted infections (STIs).14 Among teens, risky sexual activity can include initiating sexual activity before age 14, inconsistent or ineffective use of contraception, having multiple sexual partners, and engaging in sexual activity under the influence of substances.15,16 Research examining links between substance use and risky sexual activity has considered marijuana, alcohol, and other drugs (i.e., narcotics, opiates, amphetamines, stimulants). Given the prominence of substance use in the literature, the next section examines how substance use contributes to unintended teen pregnancy risk and why peer influence matters as a prevention strategy.17
Substance Use and Unintended Teen Pregnancy
Research suggests that substance use may increase risky sexual activity and related outcomes—including unintended teen pregnancy—in several ways, although the relationship between substance use and risky sexual activity is shaped by multiple connected factors.18 For instance, personality or individual differences (e.g., impulsivity, self-efficacy, sensation-seeking), contextual factors (e.g., social norms, where behaviors take place), and interpersonal factors (e.g., family, peers) all play a role in a young person’s decision-making around substance use and sexual activity.19 Research with youth points to several ways that substance use may contribute to risky sexual activity, including links to impaired judgment (i.e., while “under the influence”), decision-making during sexual interactions,20,21 and inconsistent contraceptive use.22 Substance use is also associated with intimate partner violence.23
Impaired judgment and decision-making

Substance use is associated with greater sexual risk-taking during adolescence.24 Research on adolescent brain development suggests that the prefrontal cortex, the region of the brain that regulates impulse control and decision-making, is not fully developed until the mid- to late 20s, indicating that youth are still developing their abilities to control impulses, think through and make safe decisions, and engage with others about those decisions.25 Impaired impulse control may be magnified when youth use substances.26 Specifically, alcohol and drug use may contribute to risky sexual activity by impairing judgment, inhibition, and rational decision-making among youth.27 Alcohol can act as a catalyst for risky sexual activity, with some youth describing it as “liquid courage”.28 Further, substance use has been associated with sexual initiation before age 14,29 and with teen pregnancy.30
Inconsistent or ineffective contraceptive use
Substance use is associated with inconsistent or ineffective use of contraceptives,31,32,33 but this relationship is complex and not always direct. For example, higher levels of alcohol use are associated with lower levels of condom use.34 However, substance use can influence behavior in ways that lead to improper or incorrect use of contraception, which can increase the risk of teen pregnancy (e.g., missed doses of hormonal contraception or incorrect condom use).35 Additionally, substance use may impair judgment and decision-making in the moment, making it harder for young people to consider sexual risks and take steps to protect themselves.36,37
Substance use, intimate partner violence, and reproductive coercion
Although the focus of this research synthesis is not sexual violence, we acknowledge the serious risks associated with substance use and experiences of dating or intimate partner violence. Substance use may exacerbate intimate partner violence and reproductive coercion, both of which are associated with the risk of teen pregnancy.38,39 However, it is important to note that while violence and substance use may occur in the same environments, substance use is not necessarily the root cause of violence. Experiencing intimate partner violence is associated with an increased risk of unintended pregnancy, including when a partner uses coercion, manipulation, or threats related to sex and pregnancy.40,41 Reproductive coercion can occur when an individual or their sexual partner directly interferes with or sabotages contraception to reduce its effectiveness (e.g., not using or improperly using condoms, withholding hormonal contraceptives).42 These actions undermine individual decision making and may increase the likelihood of unintended pregnancy. Some research has shown that girls and young women with current or previous foster care involvement report experiencing reproductive coercion (e.g., a sexual partner told them to not use hormonal birth control, took away their hormonal birth control, prevented them from going to a clinic, refused to use or deliberately damaged a condom) at higher rates than their peers.43
Importantly, substance use often occurs within social contexts that shape youth’s decisions, including peers’ perceptions and behaviors surrounding substance use, as well as direct peer pressure. These influences are particularly important during adolescence, when peer norms can strongly affect decision making.44,45 At the same time, peer influence is associated with attitudes toward and engagement in risky sexual activity, further compounding risk.46
Peer Influence on Substance Use and Risky Sexual Activity
During adolescence and young adulthood, peer influence can shape both substance use and sexual activity.47,48 Given the potential for unstable adult support systems, peer influences may be particularly important to consider for youth experiencing the child welfare and/or juvenile justice systems, or homelessness.49,50,51,52
Peer influence on substance use
Substance use behaviors can be shaped by direct peer influence (e.g., peer pressure) and perceived peer influence (e.g., beliefs about what one’s peers are doing).53 Youth often adjust their substance use behavior to align with both the actual behavior of their peers and their perceptions of peer behavior.54 For example, youth may have inaccurate beliefs about the prevalence of substance use among their peers, which can influence their own decision-making (e.g., thinking, “All my peers are drinking, so I should too”).55,56 Research indicates that youth commonly overestimate peer alcohol use, and these inflated perceptions are associated with a higher likelihood of alcohol use.57
Peer influence on substance use can vary depending on the type or closeness of the peer relationship, including relationships with close friends and romantic partners versus acquaintances or broader peer networks. Close friends tend to shape behavior through shared norms, expectations, and day-to-day social interactions, while broader peer groups influence behavior through perceived norms and social desirability.58 For example, if members of a close friend group regularly drink at parties and view this behavior as typical, other member may feel increased pressure to engage in similar behaviors. In contrast, a young person may believe that “most people at my school are hooking up and not using condoms,” based on social media posts, rumors, or high-visibility peers. Even without direct pressure, perceptions about what is common or socially accepted can influence behavior to align with perceived norms.
Example: If a young person’s close friends regularly drink at parties, they may feel pressure to join them.
Takeaway: What feels normal in a friend group can shape a young person’s choices about drinking and sex.
Peer influence on substance use may be especially important for youth whose relationships with supportive adults are limited or unstable, such as youth who experience the child welfare system, juvenile justice system, or homelessness. A qualitative study of youth between ages 16 to 21 who were experiencing homelessness found that social networks shape substance use norms through shared patterns of use, perceptions of drug-related safety, encouragement or discouragement of use, and beliefs about when and where substance use is socially acceptable.59 For youth transitioning out of foster care, exposure to peer groups engaging in risky activities and exposure to broader neighborhood-level stressors were identified as risk factors for using multiple substances, even after accounting for family and other supports.60 Similarly, among young people experiencing homelessness who had previously been in foster care (average age: 22), a greater number of foster care placements was associated with an increased likelihood of having peers who used methamphetamine in their social networks.61 This finding highlights how placement instability may disrupt stable, supportive relationships and contribute to greater reliance on peer networks in which substance use is more prevalent, thereby increasing the risk of substance use.62 Finally, among youth involved in the juvenile justice system, both family and peer substance use have been shown to increase the risk of alcohol and illicit drug use, through direct exposure to substances and the development of “pro-drug” attitudes.63 Pro-drug attitudes refer to beliefs that substance use is common, socially acceptable, or low risk (e.g., “Everyone drinks” or “It’s not a big deal”), often shaped by perceived peer norms and perceived approval of use.64,65
Collectively, this body of research highlights peers as a central influence on substance use, particularly among youth experiencing different types of instability and system involvement.
Peer influence on sexual behaviors
Peer influence on adolescent and young adult sexual activity operates through both direct peer pressure and indirect peer influence (e.g., peer norms and expectations about what sexual behaviors are typical or socially acceptable).66 For example, a recent meta-analysis examining peer norms and adolescent sexual activity highlighted the multiple ways peers shape risky sexual activity.67 Research indicates that youth are more likely to engage in sexual activity when they perceive that their peers are sexually active, approve of sex, or pressure them to engage in sexual activity. The same study found that these associations are strongest when youth perceive these norms among close friends rather than broader peer groups.68
Notably, beliefs about what peers do (i.e., descriptive norms) have been found to be more strongly associated with sexual activity than beliefs about what peers approve of (i.e., injunctive norms) or direct peer pressure related to sex. This suggests that adolescents may be more influenced by observed or assumed peer behaviors than by explicit expectations or verbal encouragement.
Peer influence is particularly important for youth in the child welfare or juvenile justice systems or youth experiencing homelessness because they rely more heavily on peers for support. Among youth who had experienced maltreatment, earlier pubertal development (ages 9 to 13) was associated with engagement with peers who used substances (i.e., alcohol or marijuana), which, in turn, was associated with an increased risk for substance use and sexual activity.69 Similarly, among youth experiencing homelessness, those whose networks include people with multiple simultaneous partners or who engage in unsafe sex are more likely than their peers whose networks do not include people engaging in these behaviors to have multiple simultaneous partners or engage in unsafe sex.70 Youth who experienced homelessness prior to exiting foster care, compared to those who did not experience homelessness, are more likely to be connected to peers who engage in risky sexual activity including sex without a condom.71
Conversely, perceived peer use of condoms during sexual activity is associated with lower risk. Among youth experiencing homelessness, perceiving higher levels of peer condom use or safer sex practices is associated with reduced odds of engaging in sex without a condom.72 Regarding pregnancy-related attitudes, youth experiencing homelessness who perceive their “street-based peers” (i.e., peers also experiencing homelessness) or serious romantic partners as disapproving of pregnancy, compared to approving of pregnancy, are significantly less likely to endorse positive attitudes toward becoming pregnant.73
Together, these findings suggest that peer and partner norms—both risk-promoting and protective—play a significant role in shaping adolescents’ sexual activity and pregnancy-related attitudes.
Increasing Positive Peer Influence and Interrupting the Link Between Substance Use and Risky Sexual Behavior
Positive peer norms and support
Peers can play a protective role by reinforcing safer norms and expectations related to sexual activity and substance use. Youth whose peer networks both promote safer sexual practices (e.g., contraception use, non-judgmental attitudes toward abstinence, and norms supportive of delaying sexual activity) and discourage substance use engage in risky sexual behaviors at lower rates, underscoring the protective role of positive peer influence.74,75,76 In one study, having someone to talk to when feeling sad was associated with lower levels of risk-taking behaviors among youth who are stably housed, including substance use and sexual activity. However, among youth experiencing housing instability, the same form of social support was associated with higher levels of risk-taking behaviors, suggesting that the protective function of support may depend on broader contextual factors.77 Taken together, this body of research suggests that peer influence can contribute to increased risk when peers model or reinforce risky activity, but can also serve as a protective factor when peers model and promote safer activity and contribute to supportive norms.
Using peer leaders in substance use and teen pregnancy prevention programming
The research presented above suggests that peers may play a valuable role in programming focused on substance use and teen pregnancy prevention. For youth who experience the child welfare or juvenile justice systems, or youth experiencing homelessness, peer influence may be especially important because relationships with supportive adults or caregivers may be disrupted by instability or system involvement. For example, a study of adolescent girls in a residential care setting found that girls in the sample had stronger ties to peers than to caregivers and that these peer relationships were sometimes associated with negative influences on substance use and sexual activity.78 At the same time, this research provides support for the idea of using positive peer networks as a prevention approach to minimize substance use and risky sexual activity that can lead to unintended teen pregnancy.79 For example, adolescents and young adults who model or encourage substance-free behaviors can discourage alcohol and drug use among their peers.80,81 Peer influence was a key factor in the success of an alcohol and tobacco use prevention program across a large sample of adolescents.82 In a study that gathered input on intervention strategies for preventing unintended pregnancy and STIs directly from youth in foster care, youth supported the inclusion of peer facilitators who shared past experiences and helped build positive peer networks.83 Collectively, these findings suggest that youth may benefit from programming that includes peer leaders who engage them in dialogue and counter direct or perceived negative peer pressure.
The resources below provide more information on implementing peer facilitation into your work with youth:
- Peer Facilitation: Accelerating Individual, Community, and Societal Change
- Promoting Peer Support in Child Welfare
- Advancing the Work of Peer Support Specialist in Behavioral Health-Criminal Justice Programming
- Expanding Peer Support Roles in Homeless Services Delivery: A Toolkit for Service Providers
- Perspectives on Young Parents as Peer Educators in a Teen Pregnancy Prevention Program
- Peer Education for Adolescent Reproductive and Sexual Health
- Part 1 of Peer Support Group Facilitation Skills for Peer Specialist in Veterans Health Administration
Conclusion
The literature reviewed in this summary suggests that peers can heighten the level of risk when substance use, unprotected sex, or supportive attitudes toward pregnancy are normalized within youths’ social networks. At the same time, peers can function as important protective influences when they model safer behaviors, reinforce contraception use, discourage substance use, and communicate norms that support healthier decision-making. Taken together, this research suggests that efforts to reduce unintended teen pregnancy should consider not only individual knowledge and behavior change, but also peer networks and social contexts that shape youth’s decisions. Further, because peer relationships influence both sexual activity and substance use, prevention strategies that address peer influence may help reduce substance use and the risk of unintended pregnancy. More information and practice-based strategies for working with youth to harness positive peer influence and reduce substance use and risky sexual activity are available in this related technical assistance tool: A Technical Assistance Tool for Helping Youth Navigate Peer Influence.
In sum, harnessing positive peer influence through peer-led programming, supportive social networks, and strategies that shift peer norms may be a promising way to reduce substance use, support safer sexual decision-making, and ultimately reduce the risk of unintended teen pregnancy.

