Table 1. Studies of Endorphin and Enkephalin Levels in Individuals with Autism.

Study	Fluid	Autism Group (N)	Opioid	Results
Weizman et al. 1984 [26]	Plasma	10	Humeral endorphin	Decreased compared to normals
Herman et al. 1986 [27]	Plasma	5	BE	Similar to normals
Weizman et al. 1988 [28]	Plasma	22	BE	Decreased compared to normals or schizophrenics
Bouvard et al. 1992 [29]	Plasma	4	BE	Increased compared to normals
Ernst et al. 1993 [30]	Plasma	5	BE	Similar to normals
Leboyer et al. 1994 [31]	Plasma	67	N-terminal BE	Decreased compared to normals or girls with Rett's
Leboyer et al. 1999 [32]	Plasma	62	C-terminal BE	Increased compared to normals or girls with Rett's
Bouvard et al. 1995 [33]	Plasma	10	C-terminal BE	Increased compared to normativecontrol values
Tordjman et al. 1997 [34]	Plasma	48	BE	Increased compared to normals
Brambilla et al. 1997 [35]	PBMC*	12	BE	Increased compared to normals or PDD
Cazullo et al. 1999 [36]	PBMC	11	C-terminal BE	Increased compared to normals
Gillberg et al. 1985 [37]	CSF**	20	Met-enkephalin	Increased in SIB and low pain sensitivity
Ross et al. 1987 [38]	CSF	9	BE	Increased compared to normals
Gillberg et al. 1990 [39]	CSF	31	BE	Decreased compared to normal adults
Nagamitsu et al. 1993 [40], 1997 [41]	CSF	19	BE	Similar to normals

^*PBMC indicates peripheral blood mononuclear cells.

^**CSF indicates cerebrospinal fluid.