Deep brain stimulation (DBS) to the nucleus accumbens (NAcc-DBS) was associated 
with antidepressant, anxiolytic, and procognitive effects in a small sample of 
patients suffering from treatment-resistant depression (TRD), followed over 1 
year. Results of long-term follow-up of up to 4 years of NAcc-DBS are described 
in a group of 11 patients. Clinical effects, quality of life (QoL), cognition, 
and safety are reported. Eleven patients were stimulated with DBS bilateral to 
the NAcc. Main outcome measures were clinical effect (Hamilton Depression Rating 
Scale, Montgomery-Asperg Rating Scale of Depression, and Hamilton Anxiety Scale) 
QoL (SF-36), cognition and safety at baseline, 12 months (n=11), 24 months 
(n=10), and last follow-up (maximum 4 years, n=5). Analyses were performed in an 
intent-to-treat method with last observation carried forward, thus 11 patients 
contributed to each point in time. In all, 5 of 11 patients (45%) were 
classified as responders after 12 months and remained sustained responders 
without worsening of symptoms until last follow-up after 4 years. Both ratings 
of depression and anxiety were significantly reduced in the sample as a whole 
from first month of NAcc-DBS on. All patients improved in QoL measures. One 
non-responder committed suicide. No severe adverse events related to parameter 
change were reported. First-time, preliminary long-term data on NAcc-DBS have 
demonstrated a stable antidepressant and anxiolytic effect and an amelioration 
of QoL in this small sample of patients suffering from TRD. None of the 
responders of first year relapsed during the observational period (up to 4 
years).