Exemplar resources provided in the control arm will include a selection from the National Alliance on Mental Illness and Mental Health America designed to support caregivers helping loved ones access care.

Treatment facilitation / duration of untreated psychosis will be assessed according to participants' report of appointments attended by their relative in the past during the treatment period. This first category includes meeting with a clinician providing mental health therapy or counseling. At screening, participants report treatment engagement over the previous three months and during the study period, participants are asked to report on this weekly. This count variable represents the number of participants who reported that their loved one attended an appointment for psychotherapy or counseling in the three months preceding the study period reported at screening ("Baseline") as well as for the duration of the study period reported in weekly brief assessments ("12 weeks"). The 12 week data point includes participants who completed at least half of the weekly brief assessments.

Illness appraisals will be assessed with the Illness Perception Questionnaire for Schizophrenia Relatives (IPQSR), a self-report scale of caregivers' beliefs about the severity, prognosis, and responsiveness to treatment of mental illnesses. Each item is rated on a 5-point scale (1 = strongly disagree; 5 = strongly agree), and totals are scored by summing individual items. For the coherence total, we are totaling the 5 items related to the caregiver's report of how much they understand or know about their loved one's illness. Scores range from 5 to 25 with lower scores indicating better self-rated understanding or coherence.

Illness appraisals will be assessed with the Illness Perception Questionnaire for Schizophrenia Relatives (IPQSR), a self-report scale of caregivers' beliefs about the severity, prognosis, and responsiveness to treatment of mental illnesses. Each item is rated on a 5-point scale (1 = strongly disagree; 5 = strongly agree), and totals are scored by summing individual items. For the consequences total, we are totaling the 20 items related to consequences affecting the caregiver and the affected person. Scores range from 20 to 100 with higher scores indicating greater perceptions of negative consequences.

Illness appraisals will be assessed with the Illness Perception Questionnaire for Schizophrenia Relatives (IPQSR), a self-report scale of caregivers' beliefs about the severity, prognosis, and responsiveness to treatment of mental illnesses. Each item is rated on a 5-point scale (1 = strongly disagree; 5 = strongly agree), and totals are scored by summing individual items. For the control total, we are totaling the 8 items related to caregiver, affected person, and treatment control over illness course. Scores range from 8 to 40 with higher scores indicating greater perceptions of possibilities for actions that affect the course of illness.

Illness appraisals will be assessed with the Illness Perception Questionnaire for Schizophrenia Relatives (IPQSR), a self-report scale of caregivers' beliefs about the severity, prognosis, and responsiveness to treatment of mental illnesses. Each item is rated on a 5-point scale (1 = strongly disagree; 5 = strongly agree), and totals are scored by summing individual items. For the emotional distress score, we are examining the emotional representation scale, a 9-item scale with scores ranging from 9 to 45, with higher scores indicating greater emotional distress.

Appraisals of caregiving experiences will be assessed with the Brief Experience of Caregiving Inventory (BECI).** The BECI is a 19-item assessment of the impact of caregiving on the individual's life, both in negative and positive ways. The items are rated on a 5-point Likert scale (never to nearly always), and scores range from 0 to 76, with a higher score denoting more negative appraisals of one's caregiving experience.

**NOTE: The version of the BECI that was administered used instructions asking participants to report on their experiences in the month following their loved one's first hospitalization. Due to this, this measure is best interpreted as caregivers' changing appraisals of their early experiences of caregiving. There was also heterogeneity in participants' report of their loved one ever having experienced a hospitalization in our sample that also affects interpretation of this measure.

Caregiver coping will be assessed with the Brief COPE Inventory, a 28-item self-report scale of coping skills in response to stressors, based on the full COPE inventory; items generate a range of subscale scores related to specific coping areas. The instrument consists of 28 items which will be scored on a 1 to 4 Likert scale (I haven't been doing this at all to I've been doing this a lot), with higher values representing a greater frequency of engaging in each coping strategy. For this outcome, we will examine total frequency sum of items (14) assessing variables a priori selected to represent adaptive coping. Scores on this scale range from 14 to 56.

Caregiver coping self-efficacy will be assessed with the Coping Self-Efficacy Scale, a 26-item self-report questionnaire measuring the perceived ability of coping with various life challenges. Responses are rated on a 0 to 10 scale, and scores range from 0 to 260, with higher scores denoting a greater sense of self-efficacy in coping.

Caregiver distress (secondary mediator) will be assessed with General Health Questionnaire (GHQ), a 12-item questionnaire assessing general psychological morbidity. Respondents indicate agreement on a four-point scale (0 = Not at all; 3 = More than usual) and total scores ranging from 0 to 36 with higher scores indicating more severe psychological morbidity.

Participants in the control condition will be provided support resources from mental health advocacy organizations representing currently available resources for caregivers (including a selection from the National Alliance on Mental Illness and Mental Health America). They will also have access to the research team by phone for technical troubleshooting and support as necessary.

Control: Exemplar resources provided in the control arm will include a selection from the National Alliance on Mental Illness and Mental Health America designed to support caregivers helping loved ones access care.

Total of all reporting groups

Participants in the control condition will be provided support resources from mental health advocacy organizations representing currently available resources for caregivers (including a selection from the National Alliance on Mental Illness and Mental Health America). They will also have access to the research team by phone for technical troubleshooting and support as necessary.

Control: Exemplar resources provided in the control arm will include a selection from the National Alliance on Mental Illness and Mental Health America designed to support caregivers helping loved ones access care.

Treatment seeking will be measured using the Measure to Assess Steps to Service-Caregivers (MASS-CG). The MASS-CG is a 23-item self-report assessment of steps taken by the caregiver towards the attainment of mental health treatment for their loved one, including research, social support, encouragement or support of the loved one's help-seeking actions, and engagement with service provider steps. Each item is endorsed on a three-point Likert scale (0 = No, I have not done this, 1 = I have done this once or twice, 2 = I have done this multiple times). The MASS-CG is scored by summing individual items with higher scores indicating greater levels of treatment facilitation activities.

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

Treatment facilitation / duration of untreated psychosis will be assessed according to participants' report of appointments attended by their relative in the past during the treatment period. This first category includes meeting with a clinician providing psychiatric medications. At screening, participants report treatment engagement over the previous three months and during the study period, participants are asked to report on this weekly. This count variable represents the number of participants who reported that their loved one attended an appointment with a medication provider in the three months preceding the study period reported at screening ("Baseline") as well as for the duration of the study period reported in weekly brief assessments ("12 weeks"). The 12 week data point includes participants who completed at least half of the weekly brief assessments.

Participants are included in the 12 week total if they completed more than half the brief assessments during the study period.

Treatment facilitation / duration of untreated psychosis will be assessed according to participants' report of appointments attended by their relative in the past during the treatment period. This first category includes meeting with a clinician providing mental health therapy or counseling. At screening, participants report treatment engagement over the previous three months and during the study period, participants are asked to report on this weekly. This count variable represents the number of participants who reported that their loved one attended an appointment for psychotherapy or counseling in the three months preceding the study period reported at screening ("Baseline") as well as for the duration of the study period reported in weekly brief assessments ("12 weeks"). The 12 week data point includes participants who completed at least half of the weekly brief assessments.

Participants are included in the 12 week total if they completed more than half the brief assessments during the study period.

This is assessed with the Knowledge About Schizophrenia (KAST), an 18-item multiple-choice assessment examining individuals' knowledge of the etiology, symptoms, and prognosis of schizophrenia. Total scores indicate the number of correct responses, and thus range from 0 to 18.

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

Illness appraisals will be assessed with the Illness Perception Questionnaire for Schizophrenia Relatives (IPQSR), a self-report scale of caregivers' beliefs about the severity, prognosis, and responsiveness to treatment of mental illnesses. Each item is rated on a 5-point scale (1 = strongly disagree; 5 = strongly agree), and totals are scored by summing individual items. For the coherence total, we are totaling the 5 items related to the caregiver's report of how much they understand or know about their loved one's illness. Scores range from 5 to 25 with lower scores indicating better self-rated understanding or coherence.

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

Illness appraisals will be assessed with the Illness Perception Questionnaire for Schizophrenia Relatives (IPQSR), a self-report scale of caregivers' beliefs about the severity, prognosis, and responsiveness to treatment of mental illnesses. Each item is rated on a 5-point scale (1 = strongly disagree; 5 = strongly agree), and totals are scored by summing individual items. For the consequences total, we are totaling the 20 items related to consequences affecting the caregiver and the affected person. Scores range from 20 to 100 with higher scores indicating greater perceptions of negative consequences.

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

Illness appraisals will be assessed with the Illness Perception Questionnaire for Schizophrenia Relatives (IPQSR), a self-report scale of caregivers' beliefs about the severity, prognosis, and responsiveness to treatment of mental illnesses. Each item is rated on a 5-point scale (1 = strongly disagree; 5 = strongly agree), and totals are scored by summing individual items. For the control total, we are totaling the 8 items related to caregiver, affected person, and treatment control over illness course. Scores range from 8 to 40 with higher scores indicating greater perceptions of possibilities for actions that affect the course of illness.

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

Illness appraisals will be assessed with the Illness Perception Questionnaire for Schizophrenia Relatives (IPQSR), a self-report scale of caregivers' beliefs about the severity, prognosis, and responsiveness to treatment of mental illnesses. Each item is rated on a 5-point scale (1 = strongly disagree; 5 = strongly agree), and totals are scored by summing individual items. For the emotional distress score, we are examining the emotional representation scale, a 9-item scale with scores ranging from 9 to 45, with higher scores indicating greater emotional distress.

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

Appraisals of caregiving experiences will be assessed with the Brief Experience of Caregiving Inventory (BECI).** The BECI is a 19-item assessment of the impact of caregiving on the individual's life, both in negative and positive ways. The items are rated on a 5-point Likert scale (never to nearly always), and scores range from 0 to 76, with a higher score denoting more negative appraisals of one's caregiving experience.

**NOTE: The version of the BECI that was administered used instructions asking participants to report on their experiences in the month following their loved one's first hospitalization. Due to this, this measure is best interpreted as caregivers' changing appraisals of their early experiences of caregiving. There was also heterogeneity in participants' report of their loved one ever having experienced a hospitalization in our sample that also affects interpretation of this measure.

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

Caregiver coping will be assessed with the Brief COPE Inventory, a 28-item self-report scale of coping skills in response to stressors, based on the full COPE inventory; items generate a range of subscale scores related to specific coping areas. The instrument consists of 28 items which will be scored on a 1 to 4 Likert scale (I haven't been doing this at all to I've been doing this a lot), with higher values representing a greater frequency of engaging in each coping strategy. For this outcome, we will examine total frequency sum of items (14) assessing variables a priori selected to represent adaptive coping. Scores on this scale range from 14 to 56.

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

Caregiver coping self-efficacy will be assessed with the Coping Self-Efficacy Scale, a 26-item self-report questionnaire measuring the perceived ability of coping with various life challenges. Responses are rated on a 0 to 10 scale, and scores range from 0 to 260, with higher scores denoting a greater sense of self-efficacy in coping.

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

Caregiver distress (secondary mediator) will be assessed with General Health Questionnaire (GHQ), a 12-item questionnaire assessing general psychological morbidity. Respondents indicate agreement on a four-point scale (0 = Not at all; 3 = More than usual) and total scores ranging from 0 to 36 with higher scores indicating more severe psychological morbidity.

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

Participants in the control condition will be provided support resources from mental health advocacy organizations representing currently available resources for caregivers (including a selection from the National Alliance on Mental Illness and Mental Health America). They will also have access to the research team by phone for technical troubleshooting and support as necessary.

Control: Exemplar resources provided in the control arm will include a selection from the National Alliance on Mental Illness and Mental Health America designed to support caregivers helping loved ones access care.