The invention features methods for the treatment of one or more symptoms of microcephaly associated autism disorders e.g., Christianson syndrome, by administering agents that increase the level or activity of BDNF or TrkB in the brain of the patient. These agents may include BDNF, a BDNF agonist, a BDNF mimetic, a TrkB agonist, a cell expressing recombinant BDNF, a BDNF encoding recombinant nucleic acid molecule encapsidated within a recombinant virus, and an agent that decreases the acidity of endosomes.
