This is a Study to Determine the Antidepressant Effects of AZD6765

Montgomery-Asberg Depression Rating Scale (MADRS) is a 10-item instrument used for the evaluation of depressive symptoms. Each item is rated on a scale of 0 to 6 (with higher scores indicating more severe depression). The individual item scores are added together to form a total score, ranging between 0 and 60. 0 is considered the best score, 60 the worst.

Time frame: 60 minutes (min) prior to dosing (baseline); and 60 min, 80 min, 110 min, 230 min, 1 day, 2 days, 3 days and 7 days following dosing.

Population: ITT population including all randomized patients who were given study treatment.

Beck Depression Inventory (BDI) is a 21-question instrument for measuring the severity of depression. Each question has a set of at least four possible answer choices, ranging in intensity. A value of 0 to 3 is assigned for each answer and the total score is computed. Higher total scores indicate more severe depressive symptoms.

Time frame: 60 minutes (min) prior to dosing (baseline); and 60 min, 80 min, 110 min, 230 min, 1 day, 2 days, 3 days and 7 days following dosing.

Population: ITT population including all randomized patients who were given study treatment.

Brief Psychiatric Rating Scale (BPRS) Positive is a 4-item scale which measures positive symptoms of schizophrenia (conceptual disorganization, hallucinatory behavior, suspiciousness, and unusual thought content). Each item is rated from 1 to 7 with higher score indicating greater severity. The total score is the sum of the 4 items, resulting in a range of scores from 4-28.

Time frame: 60 minutes (min) prior to dosing (baseline); and 60 min, 80 min, 110 min, 230 min, 1 day, 2 days, 3 days and 7 days following dosing.

The Brief Psychiatric Rating Scale (BPRS) is a 18-item scale which measures symptoms and behaviors that are characteristic of schizophrenia. Each item is rated from 1 to 7 with higher score indicating greater severity. The total score is the sum of the 18 items, resulting in a range of scores from 18-126. 18 is considered to be the best outcome, 126 the worst.

Time frame: 60 minutes (min) prior to dosing (baseline); and 60 min, 80 min, 110 min, 230 min, 1 day, 2 days, 3 days and 7 days following dosing.

Population: ITT population including all randomized patients who were given study treatment.

Clinician- Administered Dissociative States Scale (CADSS) is a clinician-administered measure of perceptual, behavioral, and attentional alterations occurring during dissociative experiences. This scale involves a 23 questions and each is rated from 0 (not at all) to 4 (extremely). The total score is sum of the 23 items and range from 0 to 92 - best is 0 and worst is 92.

Time frame: 60 minutes (min) prior to dosing (baseline); and 60 min, 80 min, 110 min, 230 min, 1 day, 2 days, 3 days and 7 days following dosing

Population: ITT population including all randomized patients who were given study treatment.

Hamilton Anxiety Rating Scale (HAM-A) is used as a rating measure of anxiety severity. The scale consists of 14 items. Each item is rated on a scale of 0 to 4. The HAM-A total score is the sum of the 14 items and the score ranges from 0 to 56. 0 is considered the best outcome, 56 the worst.

Time frame: 60 minutes (min) prior to dosing (baseline); and 230 min, 1 day, 2 days, 3 days and 7 days following dosing.

Hamilton Depression Rating Scale-17 item (HDRS) is a scale that assesses depressive symptoms. HDRS consists of 17 symptoms, each of which is rated from 0 to 2 or 0 to 4, where 0 is none/absent. The total score is calculated as the sum of the 17 individual symptom scores; the total score can range from 0 to 52. Higher scores indicate more severe depression.

Time frame: 60 minutes (min) prior to dosing (baseline); and 60 min, 80 min, 110 min, 230 min, 1 day, 2 days, 3 days and 7 days following dosing

Population: ITT population including all randomized patients who were given study treatment.

Scale for Suicide Ideation (SSI) is a 19-item scale designed to quantify the intensity of current conscious suicide ideation. Each item is rated on a scale of 0 to 2 (with higher scores indicating greater suicidal ideation). The individual item scores are added together to form a total score, ranging between 0 and 38. 0 is considered the best outcome, 38 the worst.

Time frame: 60 minutes (min) prior to dosing (baseline); and 60 min, 80 min, 110 min, 230 min, 1 day, 2 days, 3 days and 7 days following dosing.

Population: ITT population including all randomized patients who were given study treatment.

Response defined as a \>= 50% reduction from baseline in MADRS total score. MADRS is a 10-item instrument used for the evaluation of depressive symptoms. Each item is rated on a scale of 0 to 6 (with higher scores indicating more severe depression). The individual item scores are added together to form a total score, ranging between 0 and 60. 0 is considered the best score, 60 the worst.

Time frame: 60 minutes (min) prior to dosing (baseline); and 60 min, 80 min, 110 min, 230 min, 1 day, 2 days, 3 days and 7 days following dosing.

Population: ITT population including all randomized patients who were given study treatment.

Remission defined as a Montgomery-Asberg Depression Rating Scale (MADRS) total score \<10. MADRS is a 10-item instrument used for the evaluation of depressive symptoms. Each item is rated on a scale of 0 to 6 (with higher scores indicating more severe depression). The individual item scores are added together to form a total score, ranging between 0 and 60. 0 is considered the best score, 60 the worst.

Time frame: 60 minutes (min) prior to dosing (baseline); and 60 min, 80 min, 110 min, 230 min, 1 day, 2 days, 3 days and 7 days following dosing.

Population: ITT population including all randomized patients who were given study treatment.

The Visual Analog Scale (VAS) Anxious is a 0 to 100-mm self-administered scale where patients rate their mood between extreme sad (0-mm) and extreme happy (100-mm), with a median normal point.

Time frame: 60 minutes (min) prior to dosing (baseline); and 60 min, 80 min, 110 min, 230 min, 1 day, 2 days, 3 days and 7 days following dosing.

Population: ITT population including all randomized patients who were given study treatment.

The Visual Analog Scale (VAS) Depressed is a 0 to 100-mm self-administered scale where patients rate their mood between extreme sad (0-mm) and extreme happy (100-mm), with a median normal point.

Time frame: 60 minutes (min) prior to dosing (baseline); and 60 min, 80 min, 110 min, 230 min, 1 day, 2 days, 3 days and 7 days following dosing

Population: ITT population including all randomized patients who were given study treatment.

Young Mania Rating Scale (YMRS) consists of 11 items, rated on a scale from 0 (symptom not present) to 8 (symptom extremely severe) or from 0 (symptom not present) to 4 (symptom extremely severe). The YMRS total score ranges from 0 to 60. 0 is considered to be the best outcome, 60 the worst.

Time frame: 60 minutes (min) prior to dosing (baseline); and 60 min, 80 min, 110 min, 230 min, 1 day, 2 days, 3 days and 7 days following dosing.

Population: ITT population including all randomized patients who were given study treatment.