It may be one of the more potent symptomatic approaches.
However, keep in mind that excess aminos (some more than others) can be harmful, especially with long-term use, and may interact with drugs. For a starter, see:
One of many examples: while the amino acid, taurine has been used successfully to calm many bipolar manias, in people who are zinc-depleted (e.g. pyrolurics, many histapenics, many under stress, etc.) it can be counterproductive, actually increasing agitation.
So attention to the entire nutrient/health picture is imperative (methylation imbalances, pyrrole disorder, oxidative stress, hormonal issues, neurological problems, metal metabolism dysfunction, second messenger dysfunction, allergies, toxins, nutrient dependencies, depletion or overload, etc., as dictated by individual needs.
For more on these conditions, see Natural Healing for Bipolar Disorder, and meanwhile, stay tuned!
See also Nutritional Therapies for Bipolar, and Biochemical Individuality