It is important to note that although sleep latencies are typically short in idiopathic hypersomnia, the clinical severity may not correlate closely with the MSLT results. In fact, "latencies above 5 minutes are not uncommon in patients with clinically severe hypersomnia."[2] When sleep latency is below 10 minutes, the presence of sleep-onset REM periods (SOREMPs) in two or more of the MSLT naps suggests a diagnosis of narcolepsy, whereas sleep periods lacking rapid eye movement (NREM sleep) in the various naps suggests a diagnosis of idiopathic hypersomnia.[20] However, the importance of this differentiation between REM and NREM has been called into question.[11] (see Classification)