yes, it's true. you can gain relief from nutritional sources for depression and even the symptoms of personality disorders in addition to the usual medication.
Omega-3 Fatty Acid Treatment of Women With Borderline Personality Disorder: A Double-Blind, Placebo-Controlled Pilot Study -- Zanarini and Frankenburg 160 (1): 167 -- Am J Psychiatry
In fact, in combination with 5-HTP and tyrosine, you can reduce or eliminate the need for neuroleptics. The only drawback is economics: it is cheaper to use benzodiazepines, antidepressants and antipsychotic drugs than to nutritionally treat the underlying subclinical malnutrition.
Yet, it is unknown if the use of drugs results in a longer path to recovery than nutrition alone since no study has been done to compare the outcome of drugs and psychotherapy with nutrition and psychotherapy.