Table 2.

Design and methodologic rigor for studies of psychological/behavioral interventions in emerging adults.

Study	Level of evidence GRADE	Design	Internal validity JBI and USPTF	External validity JBI and USPTF	Limitations
Álvarez-Melcón et al. (62)	II	Randomized Control Trial (Parallel Groups)	Fair	Fair	Internal validity: Inability to blind participants and providers to intervention; effects of other treatments including medication not provided; possible confound (baseline male-female ratio difference between groups) not controlled for (note-combined had higher female so unlikely to influence results reported); intervention fidelity not provided. External validity: Only generalizable to college students with TTH diagnosed by a doctor and meeting IHS criteria, and without high state-trait anxiety. Results may not generalize to other types of relaxation training or to other therapists.
Evans et al., (60)	II	Randomized Controlled Trial (Parallel Groups)	Fair	Fair	Internal validity: Inability to blind participants and providers to intervention; effects of other treatments including medication and yoga practice at home not provided; effects of other medical conditions not provided; possible confound (baseline difference in RA duration) was statistically controlled; attendance during intervention not provided; 10 practiced at home during intervention, at FU 6 still practicing yoga. External validity: Small sample size, results only generalizable to females with RA for at least 6 months, to Iyengar yoga, with reported sequences of yoga poses, and to yoga in a college yoga clinic.
Evans, et al., (61)	II	Randomized Controlled Trial (Parallel Groups)	Poor	Fair	Internal validity: Inability to blind participants to their treatment assignment; lack of an active control group; differential attrition between groups; effects of other treatments including medication and yoga practice in TAU group not provided; effects of other medical conditions not provided; number of sessions attended by YA was 8.8/12 (73.33%); low rate of home practice at 2-month follow-up. External validity: Small sample size, results only generalizable to patients with IBS, to Iyengar yoga with reported sequences of yoga poses, and to yoga in a college yoga clinic.
Martin et al., (65)	II	Quasi-experimental	Poor	Poor	Internal validity: Inability to blind participants to their treatment assignment; lack of control group; only one measurement per period, treatment fidelity reported at 60% at least weekly use. External validity: Small sample size; only 64% of families agreed to participate; results only generalizable to patients with NF, to manualized ACT treatment in college classrooms or public settings

ACT, acceptance and commitment therapy; GRADE, grading of recommendations assessment, development, and evaluation; IBS, irritable bowel syndrome; IHS, international headache society; IMMPACT, methods, measurement and pain assessment in clinical trials; JBI, Joanna briggs institute; NF, Neurofibromatosis; USPTF, U.S. preventive services task force; RA, rheumatoid arthritis; TAU, treatment as usual; TTH, tension type headache.