Table 3 Key characteristics of the six randomised trials

Behavioural activation

 Parra et al. [45] (2019)

Colombia

Inclusion:

Psychology students aged 18 or more who scored 36 or more on the SDS

Exclusion:

- Participants who received psychological or pharmacological intervention

- Participants who used psychoactive substances

Intervention:

Single-session behavioural activation

Control:

Waitlist control

SDS

Design:

RCT

Follow-up:

2, 4 weeks

There was a significant difference between groups at 2-week follow-up, but not at 4-week follow-up

- SDS at 2 weeks: U Mann–Whitney = 311.000 (p = .03), Cohen's d = 0.74

- SDS at 4 weeks: U Mann–Whitney = 363.000 (p = .19)

 READ et al. [46] (2016)

Australia

Inclusion:

Family/Non-family carers who met the carer criteria of the Carers Recognition Act 2004

Exclusion:

Participants with depressive episodes

Intervention:

Single-session behavioural activation

Control:

Waitlist control

DASS-21

- DASS-Depression

- DASS-Anxiety

Design:

RCT

Follow-up:

2 weeks

1. There were no significant group x time effects in DASS-Depression and DASS-Anxiety, indicating no significant intervention effect in improving depression and anxiety

- DASS-Depression: Group x time (F) = 0.72, Partial eta-squared = 0.06

- DASS-Anxiety: Group x time (F) = 0.98, Partial eta-sqaured = 0.06

2. Adherence rate^c

- 56%

 Nasrin et al. [47] (2016)

United Kingdom

Inclusion:

Primary care counselling services attendees aged 18 to 60 who met major depressive disorder diagnostic criteria (using SCID-I) and who scored above 10 on the PHQ-9

Exclusion:

- Participants who received regular psychological intervention

- Participants with particular mental conditions (e.g., self-harm, psychosis, mania, eating disorder)

Intervention:

Single-session behavioural activation

Control:

Waitlist control

PHQ-9

Design:

RCT

Follow-up:

1 week

1. There was a significant difference between groups

- PHQ-9: Group (F) = 16.03 (p = .000), Eta-sqaured = 0.30

2. Adherence rate

- 51.4%

 Gawrysiak et al. [48] (2009)

United States

Inclusion:

Introductory psychology students aged 18 or more who scored 14 or more on the BDI-II

Exclusion:

- Participants who received psychological or pharmacological intervention for depression

- Participants who had received psychotherapy within the last 2 years

- Participants with high suicide risk, psychotic symptoms, or bipolar disorder

Intervention:

Single-session behavioural activation

Control:

No-treatment control

BDI-II

BAI

Design:

RCT

Follow-up:

2 weeks

1. There was a significant group x time effect in BDI-II, but not in BAI

- BDI-II: Group x time (F) = 12.54 (p < .01), Cohen's d = 1.61

- BAI: Group x time (F) = 1.42 (p = .25), Cohen's d = 0.36

2. Adherence rate

- 72%

Dialectical behaviour therapy

 Ward-Ciesielski et al. [49] (2017)

United States

Inclusion:

Participants aged 18 or more who scored 10 or more on the SSI

Exclusion:

- Participants who received psychiatric intervention during the 1 month before the screening

- Participants with severe cognitive impairment

Intervention:

Single-session dialectical behaviour therapy-brief suicide intervention

Control:

Single-session relaxation training

PHQ-9

BAI

Design:

RCT

(Active control)

Follow-up:

1, 4, 12 weeks

There was a significant main effect of time in PHQ and BAI, but when it comes to the condition and time-by-condition, the main effect was not significant. It means that both conditions improved those symptoms, but the evidence of a difference in effect between them did not exist

- PHQ-9: Time (F) = 7.68 (p < .05), Condition (F) = 1.05, Condition x Time (F) = 0.16, Cohen's d = 0.61 (baseline to 12wk)

- BAI: Time (F) = 10.41 (p < .05), Condition (F) = 1.05, Condition x Time (F) = 0.34, Cohen's d = 0.59 (baseline to 12wk)

Solution-focused psychotherapy

 Sundstrom [50] (1993)

United States

Inclusion:

Female college students who scored 10 to 29 on the BDI

Exclusion:

Participants who received psychological or pharmacological intervention for depression

Intervention:

Single-session solution-focused psychotherapy

Control:

Single-session problem-focused psychotherapy

BDI

DACL

Design:

RCT

(Active control)

Follow-up:

7–10 days

Both single-session therapies showed a significant change in BDI and DACL, but there were no significant differences in changing BDI and DACL between the two therapies

- BDI: Time (F) = 34.32 (p = .0001), Treatment (F) = 0.01 (p = .9299), Time x Treatment (F) = 0.18 (p = .8345), Cohen's d = 1.05

- DACL: Time (F) = 31.07 (p = .0001), Treatment (F) = 1.81 (p = .1872), Time x Treatment (F) = 0.45 (p = .6403), Cohen's d = 0.69