Complex sentence: Between 1990 and 1998 he was the 2nd highest cited psychiatrist, and for the 1997-2007 decade he was ranked 4th by Thomson Reuters' "Science Watch".
Split into simpler sentences: Between 1990 and 1998 he was the 2nd highest cited psychiatrist. For the 1997-2007 decade he was ranked 4th by Thomson Reuters' "Science Watch".