Treatment of Adults With Generalized Anxiety Disorder Using Glutamine

Inclusion Criteria: * Outpatients with generalized anxiety disorder defined by the criteria of the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-V) * Generalized anxiety disorder is the primary psychiatric disorder. * Untreated patients or; patients treated with paroxetine, sertraline, citalopram, escitalopram, venlafaxine or duloxetine at least for 6 weeks on a stable dose; or patients treated with any benzodiazepine at least for 4 weeks on a stable dose. * Hamilton Anxiety Rating Scale score major or equal to 20 and a score major or equal to 2 on items 1 and 2 of the same scale at both screening and baseline. * Clinical Global Impression-Severity major or equal to 4 at both screening and baseline. Exclusion Criteria: * Unable to give informed consent. * Currently participating in another clinical research. * Any other psychiatric disorder not included in the Anxiety Disorders section of the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-V). Secondary diagnosis of other anxiety disorders are allowed provided the diagnosis is not more prominent than generalized anxiety disorder symptoms. * Suicide risk as assessed by the researcher at screening or baseline. * History of substance abuse in the previous six months before the screening visit. * Suffering a medically relevant or instable disease. * If woman, being pregnant at screening visit. * If woman, being breastfeeding. * A score major or equal to 20 on the Montgomery-Asberg Depression Rating Scale at screening or baseline. * As judged by a researcher, the patient might not adhere to the intervention or complete follow-up. * History of use of a banned drug in the past two weeks prior the baseline visit; three weeks in the case of monoamine oxidase inhibitors; one week in the case of fluvoxamine or a tricyclic antidepressant; two weeks for any antipsychotic and; six weeks por long-acting injectable antipsychotics. * History of use of L-glutamine the most part of the days of the previous month before the baseline visit. * History of psychotherapy treatment in the past month before the baseline visit.