Background
Smoking tends to be common habit worldwide, we explore the effect that smoking has among those with a background of brain injury and that participated in an educational intervention.
Methods
Previously trained facilitators ran an 8-week educational program that took placed in 4 continents; the program didn't create a doctor-patient relationship. Participants met once a week for 8 weeks for a 2 hour program that includes a 45 minute presentation and small group discussions with weekly assignments. The 85 question Depression and Anxiety Assessment Test (DAAT) was used to assess depression using a modified PHQ-9 (Patient Health Questionnaire), it inquired about demographics, history of brain injury, tobacco usage among other questions. The questionnaire was administered at baseline and completion. The depression was classified according into 4 categories as none (0-6), mild (7-10), moderate (11-19) or severe (20 or more). During the program they were taught various healthy lifestyle habits including nutrition, exercise, bright light, sleep, and avoiding addictive habits among other healthy habits. 
Results
From n=5,991 participants that finished the 8-week program, n=275 had a history of significant head injury, n=196 (71%) were females. The group’s mean age was 52.9 (SD 15.7). 
Those with history of head injury that were smoking at baseline were n=46 and had a mean depression score of 17.5 (SD 7.2), median 19.5, mode 24. Regarding the depression severity at baseline 13% had no depression, 6.5% mild, 30% moderate and 50% severe depression. By the end of the 8 weeks that group had a mean depression score of 9.8 (SD 6.4), median 11, mode 13. The end depression distribution was 39% none depression, 8.6% mild, 45.6% moderate and 6.5% Severe depression and 17% had quit smoking by the end. The before and after depression scores were significant with a t (45)=7.32 with a p<0.001. 

Among those that had brain injury but did not smoke at baseline were n=229, their baseline mean depression was 14.8 (SD 7.1), median 16, mode 21.The baseline depression distribution was 15% none, 17.4% mild, 35.8% moderate and 31.4% severe. By the end of the program the mean depression score of that group was 8.9 (SD 6.8), median 8, mode 2. End depression distribution of this group 44% had no depression, 17% mild, 30% moderate and 8.7% Severe. Depression scores for this group were significant with a t test(228)=14.19 with a p<.001.
Conclusion
These results seem to indicate that those who have injury and smoked seem to have more depression. The intervention benefited both groups.

Effect of tobacco smoking on mental health among those with significant brain injury