NORTH "Lite" contains the same on-demand lessons, practices and tracking features found in the "Full" NORTH mobile application but does not include help-seeking resources.

The Internalized Stigma of Mental Health Inventory, Brief (ISMI-9) will provide additional insight into the strength of participants' internalized stigma of mental illness. The ISMI-9 is a nine-item self-report short form, where each item is rated on a four-point Likert scale (1 = Strongly disagree, 4 = Strongly agree), and totaled as a mean score. Thus scores range from 1 to 4 with higher scores indicating more severe internalization of mental illness stigma.

Perceived stress will be measured using the Perceived Stress Questionnaire (PSQ), which is a 30-item, self-report questionnaire that examines the experience of stress independent of a specific and objective occasion. Items are endorsed on a four-point scale (1 = Almost never, 4 = Usually), and are summed for a total score (ranging from 30 to 120), with higher scores indicating higher levels of perceived stress.

**NOTE: At baseline, the version provided to participants included the version of the PSQ that instructing participants to report on the past "year or two" while 6-week and 12-week assessments ask participants to report on the previous "month or so." While totals are still reported (as these still provide some information about intervention effects) these numbers should be interpreted with caution and in concert with other collected measures that include items about stress levels and coping with consistent reporting periods at all time points.

The Brief Resilience Scale (BRS) will be used to assess resiliency. The BRS is a self-report form that consists of six resiliency statements that participants agree or disagree with on a five-point scale (1 = Strongly disagree, 5 = Strongly agree). Scores are totaled as a mean, and thus range from 1 to 5, with higher scores indicating greater resilience.

The Community Assessment of Psychic Experiences (CAPE-42) will be used to assess positive, negative and depressive symptoms of psychosis. The CAPE-42 is a self-report, 42 two-part item assessment that measures both the frequency of experiencing symptoms (four-point scale, 1 = Never, 4 = Almost Always) as well as the distress level (four-point scale, 1 = Not Distressed, 4 = Very Distressed) associated with each endorsed symptom. The CAPE weighted score can be calculated by summing the frequency and distress item responses. The negative subscale is 14 items and is totaled as a mean response ranging from 2 to 8, with higher scores indicating more frequent and distressing negative symptoms.

The Community Assessment of Psychic Experiences (CAPE-42) will be used to assess positive, negative and depressive symptoms of psychosis. The CAPE-42 is a self-report, 42 two-part item assessment that measures both the frequency of experiencing symptoms (four-point scale, 1 = Never, 4 = Almost Always) as well as the distress level (four-point scale, 1 = Not Distressed, 4 = Very Distressed) associated with each endorsed symptom. The CAPE weighted score can be calculated by summing the frequency and distress item responses. The depressive subscale is 8 items and is totaled as a mean response ranging from 2 to 8, with higher scores indicating more frequent and distressing depressive symptoms.

Recovery will be assessed using the Choice of Outcome in CBT for Psychoses, Short Form (CHOICE-SF). The CHOICE-SF is an 11-item self-report form developed to assess recovery-related goals for therapy. Participants rate themselves in different therapy-focused areas such as "self-confidence" or "ways of dealing with everyday stress" on a scale (0 = Worst, 10 = Best). Scores on the CHOICE-SF are totaled as mean score across all standard items, and thus range from 0 to 10 with higher scores reflecting improved recovery.

Functioning will be measured using the Sheehan Disability Scale (SDS). The SDS is a short, five-item self-report form that assesses disability and functional impairment. The total score is the sum of three items measure to what extent symptoms have disrupted different aspects of daily life on a scale (0 = Not at all, 10 = Severely), thus the scale ranges from 0 to 30 with higher scores indicating greater functional impairment.

Usability/Acceptability will be assessed with a modified version of the System Usability Scale derived from our group's previous work developing mHealth interventions. This composite measure, which comprises 26 items based on four measures - the System Usability Scale, Post Study System Usability Scale, Technology Assessment Model Measurement Scales, and Usefulness, Satisfaction and Ease Questionnaire - assesses participants' experiences with the intervention during the study period (1 = Disagree, 2 = Neutral, 3 = Agree). While this measure is often interpreted qualitatively by item, we will also compare the overall score, which will comprise an average and thus range from 1 to 3, with higher scores reflecting higher acceptability and usability.

Participants in the control arm will be provided access to the NORTH "Lite" smartphone application designed to support young adults at risk for psychosis. They will also have access to the research team by phone for technical troubleshooting and support as necessary.

NORTH "Lite": NORTH "Lite" contains the same on-demand lessons, practices and tracking features found in the "Full" NORTH mobile application but does not include help-seeking resources.

Total of all reporting groups

Participants in the control arm will be provided access to the NORTH "Lite" smartphone application designed to support young adults at risk for psychosis. They will also have access to the research team by phone for technical troubleshooting and support as necessary.

NORTH "Lite": NORTH "Lite" contains the same on-demand lessons, practices and tracking features found in the "Full" NORTH mobile application but does not include help-seeking resources.

Help-Seeking Attitudes and Stigma will be measured primarily using the Endorsed and Anticipated Stigma Inventory (EASI). The full EASI is a 40-item self-reported questionnaire with subscales measuring beliefs about mental illness, beliefs about mental health treatment, beliefs about mental health treatment seeking, concerns about stigma from loved ones, and concerns about stigma from the workplace. The subscales are scored by summing the ratings from the eight individual items in each subscale (5-point scale with 1 = Strongly disagree, 5 = Strongly agree), with lower scores indicating less stigma, and more positive attitudes towards treatment and treatment-seeking.

The Beliefs About Treatment Scale assesses individuals' beliefs about the efficacy and usefulness of mental health treatments. It is totaled as a sum, and thus scores range from 8 to 40 with higher scores indicating more stigmatizing attitudes toward treatment.

Participants are only analyzed (and total scores mean imputed) if they completed more than half the items on the scale.

Help-Seeking Attitudes and Stigma will be measured primarily using the Endorsed and Anticipated Stigma Inventory (EASI). The full EASI is a 40-item self-reported questionnaire with subscales measuring beliefs about mental illness, beliefs about mental health treatment, beliefs about mental health treatment seeking, concerns about stigma from loved ones, and concerns about stigma from the workplace. The subscales are scored by summing the ratings from the eight individual items in each subscale (5-point scale with 1 = Strongly disagree, 5 = Strongly agree), with lower scores indicating less stigma, and more positive attitudes towards treatment and treatment-seeking.

The Beliefs About Treatment Seeking assesses individuals' attitudes toward seeking mental health treatments. It is totaled as a sum, and thus scores range from 8 to 40 with higher scores indicating more stigmatizing attitudes toward treatment seeking.

Participants are only analyzed (and total scores mean imputed) if they completed more than half the items on the scale.

The Internalized Stigma of Mental Health Inventory, Brief (ISMI-9) will provide additional insight into the strength of participants' internalized stigma of mental illness. The ISMI-9 is a nine-item self-report short form, where each item is rated on a four-point Likert scale (1 = Strongly disagree, 4 = Strongly agree), and totaled as a mean score. Thus scores range from 1 to 4 with higher scores indicating more severe internalization of mental illness stigma.

Participants who completed fewer than half of the items on the scale are excluded.

Perceived stress will be measured using the Perceived Stress Questionnaire (PSQ), which is a 30-item, self-report questionnaire that examines the experience of stress independent of a specific and objective occasion. Items are endorsed on a four-point scale (1 = Almost never, 4 = Usually), and are summed for a total score (ranging from 30 to 120), with higher scores indicating higher levels of perceived stress.

**NOTE: At baseline, the version provided to participants included the version of the PSQ that instructing participants to report on the past "year or two" while 6-week and 12-week assessments ask participants to report on the previous "month or so." While totals are still reported (as these still provide some information about intervention effects) these numbers should be interpreted with caution and in concert with other collected measures that include items about stress levels and coping with consistent reporting periods at all time points.

Participants are only analyzed (and total scores mean imputed) if they completed more than half the items on the scale.

The Brief Resilience Scale (BRS) will be used to assess resiliency. The BRS is a self-report form that consists of six resiliency statements that participants agree or disagree with on a five-point scale (1 = Strongly disagree, 5 = Strongly agree). Scores are totaled as a mean, and thus range from 1 to 5, with higher scores indicating greater resilience.

Participants are only analyzed (and total scores mean imputed) if they completed more than half the items on the scale.

The Community Assessment of Psychic Experiences (CAPE-42) will be used to assess positive, negative and depressive symptoms of psychosis. The CAPE-42 is a self-report, 42 two-part item assessment that measures both the frequency of experiencing symptoms (four-point scale, 1 = Never, 4 = Almost Always) as well as the distress level (four-point scale, 1 = Not Distressed, 4 = Very Distressed) associated with each endorsed symptom. The CAPE weighted score can be calculated by summing the frequency and distress item responses. The positive subscale is 20 items and is totaled as a mean response ranging from 2 to 8, with higher scores indicating more frequent and distressing positive symptoms.

Participants are only analyzed (and total scores mean imputed) if they completed more than half the items on the scale.

The Community Assessment of Psychic Experiences (CAPE-42) will be used to assess positive, negative and depressive symptoms of psychosis. The CAPE-42 is a self-report, 42 two-part item assessment that measures both the frequency of experiencing symptoms (four-point scale, 1 = Never, 4 = Almost Always) as well as the distress level (four-point scale, 1 = Not Distressed, 4 = Very Distressed) associated with each endorsed symptom. The CAPE weighted score can be calculated by summing the frequency and distress item responses. The negative subscale is 14 items and is totaled as a mean response ranging from 2 to 8, with higher scores indicating more frequent and distressing negative symptoms.

Participants are only analyzed (and total scores mean imputed) if they completed more than half the items on the scale.

The Community Assessment of Psychic Experiences (CAPE-42) will be used to assess positive, negative and depressive symptoms of psychosis. The CAPE-42 is a self-report, 42 two-part item assessment that measures both the frequency of experiencing symptoms (four-point scale, 1 = Never, 4 = Almost Always) as well as the distress level (four-point scale, 1 = Not Distressed, 4 = Very Distressed) associated with each endorsed symptom. The CAPE weighted score can be calculated by summing the frequency and distress item responses. The depressive subscale is 8 items and is totaled as a mean response ranging from 2 to 8, with higher scores indicating more frequent and distressing depressive symptoms.

Participants are only analyzed (and total scores mean imputed) if they completed more than half the items on the scale.

Recovery will be assessed using the Choice of Outcome in CBT for Psychoses, Short Form (CHOICE-SF). The CHOICE-SF is an 11-item self-report form developed to assess recovery-related goals for therapy. Participants rate themselves in different therapy-focused areas such as "self-confidence" or "ways of dealing with everyday stress" on a scale (0 = Worst, 10 = Best). Scores on the CHOICE-SF are totaled as mean score across all standard items, and thus range from 0 to 10 with higher scores reflecting improved recovery.

Participants are only analyzed (and total scores mean imputed) if they completed more than half the items on the scale.

Functioning will be measured using the Sheehan Disability Scale (SDS). The SDS is a short, five-item self-report form that assesses disability and functional impairment. The total score is the sum of three items measure to what extent symptoms have disrupted different aspects of daily life on a scale (0 = Not at all, 10 = Severely), thus the scale ranges from 0 to 30 with higher scores indicating greater functional impairment.

Participants are only analyzed (and total scores mean imputed) if they completed more than half the items on the scale.

Usability/Acceptability will be assessed with a modified version of the System Usability Scale derived from our group's previous work developing mHealth interventions. This composite measure, which comprises 26 items based on four measures - the System Usability Scale, Post Study System Usability Scale, Technology Assessment Model Measurement Scales, and Usefulness, Satisfaction and Ease Questionnaire - assesses participants' experiences with the intervention during the study period (1 = Disagree, 2 = Neutral, 3 = Agree). While this measure is often interpreted qualitatively by item, we will also compare the overall score, which will comprise an average and thus range from 1 to 3, with higher scores reflecting higher acceptability and usability.

Participants are only analyzed if they completed more than half the items on the scale.

Participants in the control arm will be provided access to the NORTH "Lite" smartphone application designed to support young adults at risk for psychosis. They will also have access to the research team by phone for technical troubleshooting and support as necessary.

NORTH "Lite": NORTH "Lite" contains the same on-demand lessons, practices and tracking features found in the "Full" NORTH mobile application but does not include help-seeking resources.