Parent substance use was measured with the Opioid and Other Substance Use Involvement measure from the HEAL Prevention Cooperative Common Constructs. This measure assesses participants' use of alcohol, cannabis, prescription opioids, illegally manufactured opioids, and stimulants. A series of questions were asked about each substance of interest, starting with a question assessing if the parent had ever used the substance. Parents who responded "yes" received additional questions about that substance; parents who responded "no" did not. The following header was included at the beginning of the section about marijuana use: "The next questions are about marijuana. Marijuana is also called pot, weed, or cannabis. These questions DO NOT include CBD only."

Parents with prior marijuana use were asked: "During the past 30 days, how many days did you use marijuana?" Responses could range from 0-30 days. Higher scores indicate more frequent use of marijuana.

Parent substance use was measured with the Opioid and Other Substance Use Involvement measure from the HEAL Prevention Cooperative. For each substance, parents were asked if they had ever used it. Parents who responded "yes" received additional questions; parents who responded "no" did not. A header in the section about use of prescription opioids read: "This next item asks about using prescription opioids for pain relief or treatment...in any way a doctor or medical provider did not tell you to use them. This includes:

• Using without a prescription of your own (for example, someone else's medicine)
• Using more or for longer than you were told to take it
• Using for reasons other than pain (such as to get high, to sleep, or for anxiety)"

Parents with prior prescription opioid misuse were asked: "During the past 30 days, how many days did you use a prescription opioid?" Responses could range from 0-30 days. Higher scores indicate more frequent use of prescription opioids.

Parent substance use was measured with the Opioid and Other Substance Use Involvement measure from the HEAL Prevention Cooperative Common Constructs. This measure assesses participants' use of alcohol, cannabis, prescription opioids, illegally manufactured opioids, and stimulants. A series of questions were asked about each substance of interest, starting with a question assessing if the parent had ever used the substance. Parents who responded "yes" received additional questions about that substance; parents who responded "no" did not. The following header was included at the beginning of the section about illegally manufactured opioids: "The next questions ask about manufactured opioids including heroin (also called black tar, poppy, or smack) and Fentanyl."

Parents with prior use of illegally manufactured opioids were asked: "During the past 30 days, how many days did you use heroin?" Responses could range from 0-30 days. Higher scores indicate more frequent use of heroin.

Parent substance use was measured with the Opioid and Other Substance Use Involvement measure from the HEAL Prevention Cooperative Common Constructs. A series of questions were asked about each substance of interest, starting with a question assessing if the parent had ever used the substance. Parents who responded "yes" received additional questions about that substance; parents who responded "no" did not. The following header was included at the beginning of the section about use of stimulants: "The next questions ask about stimulants. Some examples of stimulants include: Adderall, Concerta, Cylert, Provigil, Ritalin or Dexedrine, speed, amphetamine, methamphetamine, uppers, bennies, pep pills, crystal, crank."

Parents with prior stimulant use were asked: "During the past 30 days, how many days did you use stimulants?" Responses could range from 0-30 days. Higher scores indicate more frequent use of stimulants.

Parental depression was measured with the Patient Health Questionnaire-9 (PHQ-9). Scores could range from 0-27; a higher score indicates greater depression.

Parental anxiety was measured with the General Anxiety Disorder-7 (GAD-7). Scores could range from 0-21; a higher score indicates greater anxiety.

Parental stress was measured with the Perceived Stress Scale. Scores could range from 0-56; a higher score indicates high perceived stress.

Parents in this arm will initially serve as the control group but will receive access to the FCU Online website after completing four waves of data collection (baseline, 3-mo, 6-mo, and 12-mo follow-up).

Total of all reporting groups

N=354 for this question, rather than N=356, because two participants in the waitlist control condition chose not to respond to this demographic question.

Parents in this arm will initially serve as the control group but will receive access to the FCU Online website after completing four waves of data collection (baseline, 3-mo, 6-mo, and 12-mo follow-up).

Parents' skill in setting limits was measured with the "setting limits" subscale of the Parenting Young Children Questionnaire (PARYC). Scores could range from 7-49; a higher score indicates greater skill in setting limits.

Number of participants differs between baseline and follow-up waves due to attrition (e.g., participants not returning surveys at follow-up waves).

Parents' skill in proactive parenting was measured with the "proactive parenting" subscale of the Parenting Young Children Questionnaire (PARYC). Scores could range from 7-49; a higher score indicates greater skill in proactive parenting.

Number of participants differs between baseline and follow-up waves due to attrition (e.g., participants not returning surveys at follow-up waves).

Parents' confidence in their parenting skills was measured with the Behavioral Self-Efficacy subscale (PAREFF) of the Parenting Tasks Checklist. Scores could range from 1-5; a higher score indicates greater parent confidence.

Number of participants differs between baseline and follow-up waves due to attrition (e.g., participants not returning surveys at follow-up waves).

Parent substance use was measured with the Opioid and Other Substance Use Involvement measure from the HEAL Prevention Cooperative Common Constructs. This measure assesses participants' use of alcohol, cannabis, prescription opioids, illegally manufactured opioids, and stimulants. A series of questions were asked about each substance of interest, starting with a question assessing if the parent had ever used the substance. Parents who responded "yes" received additional questions about that substance. Parents who responded "no" did not receive additional questions about that substance.

Parents who indicated prior alcohol use were asked: "During the past 30 days, how many days did you drink alcohol?" Responses could range from 0-30 days. Higher scores indicate more frequent use of alcohol.

Number of participants differs between baseline and follow-up waves due to attrition (e.g., participants not returning surveys at follow-up waves).

Parent substance use was measured with the Opioid and Other Substance Use Involvement measure from the HEAL Prevention Cooperative Common Constructs. This measure assesses participants' use of alcohol, cannabis, prescription opioids, illegally manufactured opioids, and stimulants. A series of questions were asked about each substance of interest, starting with a question assessing if the parent had ever used the substance. Parents who responded "yes" received additional questions about that substance; parents who responded "no" did not. The following header was included at the beginning of the section about marijuana use: "The next questions are about marijuana. Marijuana is also called pot, weed, or cannabis. These questions DO NOT include CBD only."

Parents with prior marijuana use were asked: "During the past 30 days, how many days did you use marijuana?" Responses could range from 0-30 days. Higher scores indicate more frequent use of marijuana.

Number of participants differs between baseline and follow-up waves due to attrition (e.g., participants not returning surveys at follow-up waves).

Parent substance use was measured with the Opioid and Other Substance Use Involvement measure from the HEAL Prevention Cooperative. For each substance, parents were asked if they had ever used it. Parents who responded "yes" received additional questions; parents who responded "no" did not. A header in the section about use of prescription opioids read: "This next item asks about using prescription opioids for pain relief or treatment...in any way a doctor or medical provider did not tell you to use them. This includes:

• Using without a prescription of your own (for example, someone else's medicine)
• Using more or for longer than you were told to take it
• Using for reasons other than pain (such as to get high, to sleep, or for anxiety)"

Parents with prior prescription opioid misuse were asked: "During the past 30 days, how many days did you use a prescription opioid?" Responses could range from 0-30 days. Higher scores indicate more frequent use of prescription opioids.

Number of participants differs between baseline and follow-up waves due to attrition (e.g., participants not returning surveys at follow-up waves).

Parent substance use was measured with the Opioid and Other Substance Use Involvement measure from the HEAL Prevention Cooperative Common Constructs. This measure assesses participants' use of alcohol, cannabis, prescription opioids, illegally manufactured opioids, and stimulants. A series of questions were asked about each substance of interest, starting with a question assessing if the parent had ever used the substance. Parents who responded "yes" received additional questions about that substance; parents who responded "no" did not. The following header was included at the beginning of the section about illegally manufactured opioids: "The next questions ask about manufactured opioids including heroin (also called black tar, poppy, or smack) and Fentanyl."

Parents with prior use of illegally manufactured opioids were asked: "During the past 30 days, how many days did you use heroin?" Responses could range from 0-30 days. Higher scores indicate more frequent use of heroin.

Number of participants differs between baseline and follow-up waves due to attrition (e.g., participants not returning surveys at follow-up waves).

Parent substance use was measured with the Opioid and Other Substance Use Involvement measure from the HEAL Prevention Cooperative Common Constructs. A series of questions were asked about each substance of interest, starting with a question assessing if the parent had ever used the substance. Parents who responded "yes" received additional questions about that substance; parents who responded "no" did not. The following header was included at the beginning of the section about use of stimulants: "The next questions ask about stimulants. Some examples of stimulants include: Adderall, Concerta, Cylert, Provigil, Ritalin or Dexedrine, speed, amphetamine, methamphetamine, uppers, bennies, pep pills, crystal, crank."

Parents with prior stimulant use were asked: "During the past 30 days, how many days did you use stimulants?" Responses could range from 0-30 days. Higher scores indicate more frequent use of stimulants.

Number of participants differs between baseline and follow-up waves due to attrition (e.g., participants not returning surveys at follow-up waves).

Parental depression was measured with the Patient Health Questionnaire-9 (PHQ-9). Scores could range from 0-27; a higher score indicates greater depression.

Number of participants differs between baseline and follow-up waves due to attrition (e.g., participants not returning surveys at follow-up waves). Because no families were ever lost to follow-up or withdrew from the study, all families who participated at baseline were invited to participate at each follow-up wave. Thus, there are a few families who participated at 12-month follow-up who did not participate at an earlier follow-up wave.

Parental anxiety was measured with the General Anxiety Disorder-7 (GAD-7). Scores could range from 0-21; a higher score indicates greater anxiety.

Number of participants differs between baseline and follow-up waves due to attrition (e.g., participants not returning surveys at follow-up waves). Because no families were ever lost to follow-up or withdrew from the study, all families who participated at baseline were invited to participate at each follow-up wave. Thus, there are a few families who participated at 12-month follow-up who did not participate at an earlier follow-up wave.

Parental stress was measured with the Perceived Stress Scale. Scores could range from 0-56; a higher score indicates high perceived stress.

Number of participants differs between baseline and follow-up waves due to attrition (e.g., participants not returning surveys at follow-up waves). Because no families were ever lost to follow-up or withdrew from the study, all families who participated at baseline were invited to participate at each follow-up wave. Thus, there are a few families who participated at 12-month follow-up who did not participate at an earlier follow-up wave.

Parents in this arm will initially serve as the control group but will receive access to the FCU Online website after completing four waves of data collection (baseline, 3-mo, 6-mo, and 12-mo follow-up).