The study will be a single-centre, open-label, longitudinal, pragmatic, pilot trial. Research participants at this site will be 40 men and women between the ages of 60 and 85 who have mild to moderate major depressive disorder (MDD). Participants will be recruited from primary, secondary and tertiary care centres in London, Ontario and surrounding areas. Study participation will involve 10 study visits over a total of 10 weeks. This includes 8 weekly sessions of case manager (CM) implemented Problem Solving Therapy (PST) over a period of 8 weeks and 2 clinical assessment visits pre and post intervention.

PROBLEM-SOLVING THERAPY INTERVENTION: PST is a minimally invasive treatment. This intervention will be taught in groups of approximately 10 individuals. The eight sessions of CM implemented PST will involve psychotherapy also known as talk therapy between the CM's and study participants in a group setting. Psychogeriatric interdisciplinary staff (CM's) i.e. psychiatric nurses, social workers, occupational therapists, and recreation specialists who have been previously trained in PST will function in the roles of facilitator, cofacilitator and scribe. The roles can be shared amongst the professionals to build capacity in each role or maintained over time if so desired. Sessions will be approximately one-and-a-half to two hours in length and conducted at libraries in London, ON. The first meeting will be informal in which the staff and potential group participants will be welcomed, introductions made, group rules regarding confidentiality discussed, an overview of problem solving approach described and the depression/problem solving cycle introduced. Participants will be told of the relationship between effective problem solving and changes in feelings of depression and anxiety. At the second meeting group participants will be welcomed to the initial problem solving session, group rules of confidentiality reviewed again and then each of the participants will be asked to describe important psychosocial aspects of their lives in the previous week. Facilitation will be kept to a minimum with questions designed to encourage further exploration of problems experienced. The staff person acting as the scribe shall make notes of each participant's comments. Once all the group members have checked in, the scribe shall summarize problems that have been mentioned. One of the participants will be then asked to volunteer to act as the problem solver over the next week and if there is a particular problem that they are interested in completing. Once a volunteer has identified the problem it will be listed on a flipchart and the group shall take a ten minute break. After the break, the problem will be discussed again to ensure that the correct problem has been determined. Then the goal shall be listed on the flipchart and solutions to the problem will be discussed. Once they are listed the group shall review each and note the reasons why this is a good choice and the reasons why this may not be a good choice. Considerations include effort required, time commitment, emotional impact, the need to involve others and desirability from the participants perspective. Then the participant shall narrow the options and make a decision about what solutions he/she will try in the next week. An action plan will be then developed to achieve the solutions e.g. what is the first step, when will it be made, any resources that are needed before beginning the problem solving. In addition, the participant will be asked to engage in pleasant activities on a daily basis noting the date, activity and rate how satisfied the activity made them feel on a scale of 0 to 10 with 0= Not at all and 10=Super. At the third meeting, the facilitator shall ask the participant who volunteered to solve a problem to report to the group first. That person would have made notes about their experience and use these as a reference to report back to the group. Some may make diagrams to describe their experience and share these with the group. Each session shall continue using the above format and participants will be encouraged to volunteer at least one time to practice the problem solving approach. As the group continues to meet, there will be more peer support evident as the participants begin to know each other, realize their common bonds and experience a sense of community within the group setting. The final meeting will be a time to celebrate the accomplishments of the group, listing all of the problems mentioned and those solved by the participants and an opportunity to share social time together. Participants will be asked to complete a Patient Health Questionnaire (PHQ-9) at the beginning of the initial problem solving session and continue to do so at each session. The facilitator shall comment on the changes in the scores and shall ask the participants if their experience mirrors the scores, their anxiety and depression or not. Each time point will provide an opportunity to remind the group of the depression - problem solving cycle. The CM's will teach the participant's a structured approach to cope with and resolve issues in the participant's life. Using the six stages of problem resolution including: a) identifying and clarifying the problem b) setting clear achievable goals c) brain-storming to generate solutions d) selecting a preferred solution e) clarifying steps to implement solutions, and f) evaluation. Focus will be on issues the study participant currently has in their life and not on problems from their past.

SCREENING AND INITIAL ASSESSMENTS: Potential participants will be provided a Letter of Information (LOI) and given at least 24 hours to review the letter. The Research Assistant (RA) will then contact potential participants by phone and pre-screen these participants for potential eligibility using the Patient Health Questionnaire-2 (PHQ-2). This is essential so that participants who will not be eligible do not unnecessarily travel to the hospital for screening. Those participants who score a 0 on the PHQ-2 will not be invited to a screening assessment. The screening assessment will begin with a review of the LOI, an opportunity for the potential participant to ask any questions, and a signing of the LOI by both the participant and a witness. Participants will then be screened as per inclusion and exclusion criteria by the RA, administered a Mini Mental State Exam, section A of a Mini-International Neuropsychiatric Interview (MINI), and a Hamilton Depression Rating Scale (HAM-D17). Participants meeting eligibility criteria at this point will be invited to participate in this study. This initial assessment shall also include administration of a Cumulative Illness Rating Scale for Geriatrics (CIRS-G), EuroQol 5 Dimension 5 level (EQ-5D-5L), Athena Insomnia Scale, World Health Organization Disability Assessment Schedule 2 (WHODAS-2), and a Generalized Anxiety Disorder (GAD-7). Following the final PST session participants will be asked to return for a final assessment with the RA. This post intervention assessment will include a HAM-D17, EQ-5D-5L, Athens Insomnia Scale, WHODAS-2, a GAD-7, and a likert scale to measure acceptability. At each PST session the CM's will ask participant's to complete a Patient Health Questionnaire-9 (PHQ-9) to assess changes in depressive symptoms. These questionnaires will be provided to the RA by the CM's following completion of the group's intervention, so that this data can be included in the studies final report. Following the first groups and last groups completion a focus group will be conducted. This focus group will collect qualitative data to determine long-term sustainability of PST for seniors in London, ON and surrounding area. The focus group will be lead by a research staff member who has experience with focus group interviews and qualitative study design.