A 28-year-old man with bipolar II disorder is being started on lamotrigine for depressive episode prevention. He is currently taking no other medications. The PMHNP prescribes lamotrigine 25 mg daily for the first two weeks with planned gradual titration. At week three, the patient calls stating he wants to increase the dose faster because he is still experiencing significant depressive symptoms. Which of the following best explains the rationale for maintaining the slow titration schedule?