The goal of this pilot study is to evaluate the feasibility of conducting a clinical trial assessing if ketamine infusions combined to mindfulness therapy works better than psychotherapy alone to treat chronic pain and PTSD in adults living with both conditions. The objectives of the pilot study are to 1) assess the feasibility of the trial methods and 2) assess the feasibility and tolerability of ketamine treatment in combination with psychotherapy. The main questions the future full trial would aim to answer are:

• Does the combination of ketamine infusion treatment and mindfulness therapy improve the quality of life in adults living with both chronic pain and PTSD more effectively than mindfulness therapy alone?"
• Does the combination of ketamine infusion treatment and mindfulness therapy improve disability, and depressive, PTSD and pain symptoms in adults living with both chronic pain and PTSD more effectively than mindfulness therapy alone?"
• Does implementing a brief ketamine infusion protocol safe and tolerable to treat chronic pain and PTSD?

Researchers will compare ketamine infusion treatment combined with mindfulness therapy to mindfulness therapy alone to see if the combined treatment works better to treat chronic pain and PTSD.

Participants will:

• Attend 6 visits with a research team member to complete assessments and questionnaires.
• Attend 4 ketamine treatment over 2 weeks, if allocated to the experimental group.
• Attend 8 mindfulness therapy group sessions online (1 per week).
• Log mindfulness exercises completed during the study period.

Inclusion Criteria:

i) A current DSM-5 diagnosis of PTSD (confirmed by the Mini International Neuropsychiatric Interview (66)) ii) Chronic pain (> 4/10 average pain reported for longer than 3 months (per (67)).

iii) 18-65 years of age. iv) Capacity to consent

Exclusion Criteria:

i) Currently receiving or received ketamine or psychotherapy to treat PTSD in previous 8 weeks.

ii) Meeting DSM-5 criteria for substance abuse disorder within the past month or lifetime history of ketamine abuse.

iii) Concomitant unstable major medical or neurological conditions, or laboratory/imaging results as considered by the study treating physician to interfere with trial participation (e.g. poorly controlled blood pressure, BMI >35).

iv) Pregnancy or the intention to become pregnant and breastfeeding during the study as confirmed by self-report. Participants must be willing to use a medically acceptable method of birth control which include abstinence, hormonal (birth control pills, patch, hormone injections or implants), diaphragm with spermicide or cervical cap, IUD, condom used together with spermicide, surgical sterilization (hysterectomy or partner's vasectomy) and post-menopausal more than 2 years.

v) DSM-5 diagnosis of bipolar disorder, psychotic disorder, or a severe personality disorder which may interfere with the trial. Patients with lifelong diagnosis of Bipolar Disorder, Schizophrenia or Schizoaffective disorder will be excluded. Patients with primary Obsessive Compulsive Disorder, Substance Use Disorder (dependence and abuse), Seasonal Affective Disorder, or Generalized Anxiety Disorder at time of assessment will be excluded. Primary severe borderline personality disorder and any other personality disorders that potentially may interfere with treatment administration will also be excluded.

vi) Deemed to be high suicidal risk during the baseline assessment as per treating physician. Chronic persistent suicidality is not an exclusion.

vii) Use of medications that might interfere with ketamine efficacy such as benzodiazepines with a dose equivalent to lorazepam 2mg/day or higher, and anti-convulsant (except for pregabalin and gabapentin).

viii) Deemed not appropriate to engage in group psychotherapy. ix) Inability to communicate in spoken and written English fluently enough to complete the required study assessments or a non-correctable clinically significant sensory impairment (i.e., cannot hear or see well enough to complete clinical assessments).

x) Cognitive or physical impairment severe enough to interfere with IV ketamine administration and the subject's ability to stay in the same place for a 2-hr monitoring supervision.

xi) Inability to secure a responsible adult to accompany them back home after ketamine sessions.

xii) Inability to take part in virtual care, no valid email address. xiii) Inability to safely secure IV access.