Quoting from article.
WHAT WERE THE FINDINGS?
The researchers determined that initiating clozapine treatment and duration of clozapine treatment were independent contributors of improvement in TRS symptoms. Furthermore, ROC curve analysis showed that 2.8 years was the cutoff for predicting clozapine efficacy at treating TRS symptoms.
This data showed that patients who received clozapine within 2.8 years of the onset of TRS had a treatment response rate of 81.6%. If the patient received clozapine with a greater than 2.8 years delay they had a response rate of only 30.8%. In addition, patients who received clozapine within 2.8 years were less likely to then receive electroconvulsive treatment (5%) than compared to patients who received clozapine 2.8 years after onset (23%).