The purpose of this study is to find out how meditation influences certain systems in the body: nervous system, hormonal system, and respiratory system. Another purpose is to see how meditation may help improve post-traumatic stress disorder symptoms.

This study requires nine visits to the clinic: one screening visit, one baseline visit, six training sessions, and one endpoint visit. There will be approximately 100 people enrolled in this study who will be randomly allocated to one of four groups: a slow breathing group, a meditation group, a meditation plus slow breathing group and a sitting quietly group.

Participants will undergo a telephone screening, a screening visit, baseline visit, six intervention visits (once per week for six weeks), and one endpoint visit (one week after the final training visit). A telephone screening and screening visit will ensure participant eligibility. The screening visit included structured clinician interviews on PTSD symptoms and other mental health disorders, completion of questionnaires, and receipt of home saliva collection kit. At the baseline visit, electrodes will be attached to measure the electrical activity of head, chest, skin, and respiration and blood pressure during a computer task. Intervention visits include slow breathing, meditation, mediation and slow breathing, or sitting quietly depending on which group the participant is allocated to. Breathing rates and other electrical activity of the body will be measured also. Breathing rate will be measured with an elastic band that is placed around the chest. Electrical activity will be measured by the electrodes that will be placed on the scalp, chest and skin. The endpoint visit will be exactly the same as the baseline visit.

Inclusion Criteria:

• Combat veteran (defined by a score of ≥7 on the Combat exposure scale)
• Chronic PTSD diagnosis
• Age range (25-65 years)
• Both genders
• Good general medical health
• Stable dose of medications for concurrent stable medical conditions for at least 4 weeks prior to start of the study.
• Willing and able to provide informed consent.

Exclusion Criteria:

Significant chronic medical illness including:

• current cancer treatment,
• unstable angina,
• recent myocardial infarction,
• current or past history of stroke,
• transient ischemic attack,
• congestive heart failure,
• chronic renal or hepatic failure,
• hypothyroidism

Psychiatric or behavioral illness including:

• schizophrenia,
• schizoaffective disorder,
• bipolar disorder,
• psychotic disorder (not including transient dissociative states or flashbacks associated with PTSD re-experiencing symptoms),
• any DSM-IV cognitive disorder,
• current delirium,
• psychiatric instability or situational life crises, including evidence of being actively suicidal or homicidal, or any behavior which poses an immediate danger to the patient or others.
• Substance dependence disorder within 3 months of the study or
• current substance use other than alcohol (no more than 2 drinks/day by self-report)
• Sexual assault as primary PTSD event/s.
• Planning to move from the area in the next year.
• Prior or current meditation practice.