Table 1: Evidence on PPT in healthy people and people with somatic and mental illnesses Reference Design Population Recruitment from N Control Group(s) PPT Intervention Assessment Times Results Healthy individuals and community samples Lü 201365 RCT College students with high and low trait positive affect College psychology class 34 No treatment adapted from PPT, for 16 weeks Baseline, PPT group showed a significant increase in positive trait affect Parks-Sheiner 2009 66 Study 1: RCT University students with mild-moderate depression Mass university email 110 No treatment 6-session PPT, for 6 weeks Baseline, post intervention, 3, 6 and 12 month follow-ups Significantly improved depression in intervention group post-treatment, maintained until 6-months follow-up. Significant increase in life satisfaction in both groups post-treatment Study 2: RCT Community sample Internet 361 No treatment 6-session PPT, for 6 weeks Baseline, post intervention, 1, 3, 6, 12 month follow-ups No significant results for depression, life satisfaction or positive emotion Study 3: RCT Community sample Internet 267 No treatment 6-session PPT, for 6 weeks Baseline, post intervention, 1 and 3 month follow-ups Significant decrease in depressive symptoms in PPT group post-intervention, not maintained at follow-up. Significant increase in life satisfaction in PPT group post-intervention, maintained at 1 month follow up. No significant result for positive emotions Rashid 2004 67 abstract only RCT Not stated Not stated 65 Not stated Readings, watching assigned films on character strengths, writing reaction papers weekly, class room discussions and out-of-class exercises Not stated Significant increase in character strength in intervention compared to control group Rashid 2008 68 RCT Middle school students Not stated – abstract only 22 None Not stated – abstract only Not stated – abstract only Limited description. “Substantial” change in happiness reported for the intervention group compared to control group. session
Ouweneel 2013 69 Controlled trial with to intervention or control Community sample Website 311 No treatment 25 online assignments over 8 weeks, covering three areas: happiness, and resource-building Baseline, significantly stronger increase in self-efficacy levels and positive emotions in intervention compared to control group Goodwin 2011 70 Uncontrolled study Community sample with high anxiety scores Internet, flyers, Professional referrals 11 None adapted from PPT, with 5 additional exercises, for 10 weeks Baseline, No significant changes in relationship functioning, relationship satisfaction, stress or anxiety Somatic disorders Huffman 2011 71 RCT Acute cardiovascular disease Three inpatient cardiac units 30 Active control, i.e. meditation. Attentional control, i.e. recalling events from past week 8 weekly exercises, with weekly telephone calls: (1) three good things, (2) gratitude, (3) best possible self (health), (4) best possible self (relationships), (5) and (6) three acts of kindness and (7) and (8) a repeat of one component Baseline, The PPT group showed greater improvement in depressive symptoms, anxiety, happiness and health-related quality of life compared to the two control conditions post-intervention Mental disorders Asgharipoor 201272 RCT Out-patients with major depressive disorder Referral by therapists 18 CBT 12 weekly sessions, unclear use of exercises focusing on the three domains of a good life Baseline, Significant increases in happiness in both groups.
Seligman 2006 20 Study 1: RCT Mild to students University attended – method unclear 40 Placebo therapy, i.e. recording earliest memories 6 session PPT, 6 weeks Baseline, post intervention, 3, 6, 12 month follow up The intervention group showed a significant decrease in depressive symptoms at 6 and 12 month follow up compared to control group. No significant changes in life satisfaction. Study 2: RCT Severely depressed students Referred from Counselling and Psychological Services at University of Pennsylvania 46 Two control groups: treatment as usual with or without medication 14 PPT, 12 weeks Baseline, post intervention The intervention group showed less depressive symptoms, better overall functioning, higher life satisfaction and happiness compared to both control groups post-intervention. Study 3: Uncontrolled study Community sample with depression Website 50 None Exercises from PPT: 1 exercise a month for a number of months Baseline, (tested after each exercise) Limited description. In the first month, 50 subscribers had baseline score indicating severe depression. After each completed the three blessings task and returned to the website approx. 14 days later, 94% were less depressed (mild-moderate depression) Akhtar 2010 73 Controlled trial – not stated if randomised Young adults years) with substance abuse issues Alcohol and drug treatment service for young people 20 No treatment 8 weekly sessions including savouring, gratitude, strengths, relaxation, relationships, nutrition and resilience. Baseline, 6 and 12- week follow-ups Significant increase in happiness, optimism and positive emotions post-intervention in intervention group, and decrease in happiness, optimism and positive emotions in control group. Cuadra-Peralta 2010 74 comparing PPT to existing CBT group. Outpatients with depression Mental health clinic in Chile 18 CBT 9 weekly sessions adapted from PPT Baseline, post intervention Positive psychology was more effective than behavioural therapy in decreasing depressive symptoms Huffman 2014 75 Uncontrolled study People with suicidal ideation or behaviours Inpatient psychiatric unit 61 None 9 exercises, 1 each day: gratitude, strengths, acts of kindness, meaningful Pre and post each exercise All exercises were associated with significant improvements in hopelessness and optimism, except for optimism following the forgiveness exercise (which saw a small improvement) session session