Several abnormalities in sleep architecture have been described in sch
izophrenia. However, the question of whether sleep electroencephalogra
phic (EEG) changes are influenced by treatment and phase of illness re
mains unclear. To examine the longitudinal stability of sleep data, we
compared baseline sleep measures with measures obtained approximately
4 weeks and 1 year after the beginning of treatment in a series of sc
hizophrenic patients. At the 4-week assessment, sleep continuity measu
res improved significantly; a modest increase in rapid eye movement (R
EM) latency was seen, but no other changes were found in sleep archite
cture. At the I-year assessment, REM latency, REM time, and average au
tomated REM counts increased. No significant changes were seen for slo
w-wave sleep (SWS) parameters at 1-year follow-up. These findings sugg
est that SWS parameters are relatively stable during follow-up, while
REM parameters seem to change, perhaps in relation to phase of illness
and treatment. SWS alterations may, at least in part, reflect more in
variant, perhaps trait-related alterations in schizophrenia.