Table 2.

Regression results for multilevel models estimated for each birth cohort

	1992–3			1994			1995			1996			1997
	Coefficient	(s.e.)	p Value	Coefficient	(s.e.)	p Value	Coefficient	(s.e.)	p Value	Coefficient	(s.e.)	p Value	Coefficient	(s.e.)	p Value
(Intercept)	–55.978	(1.302)	<0.001	–55.614	(1.730)	<0.001	–55.035	(1.532)	<0.001	–52.441	(1.492)	<0.001	–53.907	(1.331)	<0.001
Individual-level variables
Male	–1.201	(1.035)	0.246	1.542	(1.382)	0.265	2.127	(1.201)	0.076	0.561	(1.159)	0.628	–0.453	(1.054)	0.667
Comorbid mental retardation	1.189	(0.866)	0.170	–0.351	(1.149)	0.760	0.873	(1.050)	0.406	–1.953	(0.992)	0.049	0.839	(0.924)	0.363
Race
Asian	–2.177	(1.594)	0.172	–4.544	(1.908)	0.017	–4.169	(1.739)	0.017	–3.573	(1.614)	0.027	–3.302	(1.512)	0.029
Black	–2.319	(1.431)	0.105	–0.652	(2.063)	0.752	–3.419	(1.858)	0.066	–3.888	(1.872)	0.038	–2.645	(1.583)	0.095
Hispanic	–0.276	(1.201)	0.818	–3.130	(1.556)	0.044	–3.239	(1.397)	0.020	–2.474	(1.256)	0.049	–1.959	(1.147)	0.088
Other/missing	1.247	(3.006)	0.678	–7.285	(4.042)	0.072	–7.899	(3.897)	0.043	–3.616	(3.364)	0.282	–2.389	(2.831)	0.399
Parental education	2.152	(0.537)	<0.001	1.982	(0.661)	0.003	1.041	(0.636)	0.102	1.780	(0.557)	0.001	1.706	(0.518)	0.001
Maternal age	0.169	(0.462)	0.714	0.653	(0.604)	0.279	–0.877	(0.548)	0.109	<0.001	(0.491)	>0.999	0.357	(0.446)	0.423
Immigrant mother	–3.730	(1.112)	0.001	–0.888	(1.389)	0.522	–2.356	(1.238)	0.057	–2.494	(1.139)	0.029	–0.242	(1.025)	0.814
First born	–1.008	(0.861)	0.242	–2.342	(1.100)	0.033	–3.456	(0.984)	<0.001	–2.876	(0.901)	0.001	–0.998	(0.845)	0.237
Medi-Cal	–3.121	(1.059)	0.003	–1.216	(1.361)	0.372	–3.119	(1.249)	0.013	–1.956	(1.101)	0.076	–1.439	(1.039)	0.166
Communication	–7.887	(0.538)	<0.001	–7.246	(0.688)	<0.001	–7.371	(0.597)	<0.001	–7.512	(0.545)	<0.001	–5.460	(0.496)	<0.001
Social function	1.006	(0.500)	0.044	1.228	(0.643)	0.056	0.842	(0.570)	0.140	1.302	(0.507)	0.010	1.032	(0.477)	0.031
Repetitive behaviour	–1.197	(1.186)	0.313	0.603	(1.575)	0.702	2.019	(1.440)	0.161	–2.044	(1.362)	0.133	2.972	(1.319)	0.024
Unacceptable social behaviour	0.760	(0.806)	0.346	–0.961	(1.043)	0.357	1.500	(0.934)	0.108	0.176	(0.863)	0.838	2.105	(0.797)	0.008
Community-level variables
Child psychiatrist nearby	–0.893	(0.872)	0.306	0.516	(1.203)	0.668	–0.034	(1.081)	0.975	0.229	(0.984)	0.816	1.335	(0.866)	0.123
% College	–1.483	(0.615)	0.016	–1.639	(0.882)	0.063	–0.728	(0.732)	0.320	–0.266	(0.672)	0.692	–1.104	(0.584)	0.059
Logged median property value	1.297	(0.662)	0.050	1.991	(0.916)	0.030	2.187	(0.776)	0.005	1.069	(0.692)	0.123	1.507	(0.607)	0.013
% In poverty	0.945	(0.490)	0.054	1.234	(0.696)	0.076	0.474	(0.551)	0.390	0.679	(0.535)	0.204	0.960	(0.455)	0.035
Lagged √autism rate	0.878	(0.336)	0.009	0.077	(0.569)	0.893	1.368	(0.497)	0.006	0.986	(0.484)	0.042	1.045	(0.445)	0.019
Individuals	2277			1363			1507			1697			1867
Clusters	721	–		614			644			669			691

	1998			1999			2000			2001
	Coefficient	(s.e.)	p Value	Coefficient	(s.e.)	p Value	Coefficient	(s.e.)	p Value	Coefficient	(s.e.)	p Value
(Intercept)	–49.089	(1.120)	<0.001	–46.581	(0.979)	<0.001	–44.562	(0.766)	<0.001	–41.445	(0.629)	<0.001
Individual-level variables
Male	–0.185	(0.876)	0.833	–0.050	(0.761)	0.948	–0.559	(0.598)	0.350	–0.342	(0.496)	0.490
Comorbid mental retardation	–1.368	(0.813)	0.092	–0.069	(0.693)	0.920	–0.617	(0.577)	0.285	–0.212	(0.476)	0.656
Race
Asian	–4.060	(1.236)	0.001	–4.204	(1.069)	<0.001	–2.016	(0.850)	0.018	–1.290	(0.643)	0.045
Black	–1.180	(1.403)	0.400	–2.040	(1.194)	0.088	–2.188	(0.936)	0.019	–1.294	(0.733)	0.078
Hispanic	–2.247	(0.987)	0.023	–2.244	(0.846)	0.008	–0.618	(0.669)	0.356	–1.362	(0.516)	0.008
Other/missing	–2.825	(2.647)	0.286	–7.195	(2.328)	0.002	–2.597	(1.519)	0.087	0.080	(1.222)	0.948
Parental education	1.610	(0.449)	<0.001	1.876	(0.376)	<0.001	1.192	(0.303)	<0.001	0.798	(0.234)	0.001
Maternal age	–0.090	(0.388)	0.818	0.488	(0.335)	0.146	0.454	(0.260)	0.080	0.178	(0.215)	0.407
Immigrant mother	–0.149	(0.878)	0.865	0.810	(0.750)	0.280	–0.486	(0.598)	0.416	–0.498	(0.456)	0.275
First born	–1.461	(0.718)	0.042	0.023	(0.616)	0.970	0.410	(0.481)	0.395	–0.499	(0.389)	0.199
Medi-Cal	–1.134	(0.892)	0.204	–1.935	(0.772)	0.012	–0.933	(0.622)	0.134	–1.304	(0.474)	0.006
Communication	–5.221	(0.428)	<0.001	–3.858	(0.363)	<0.001	–3.321	(0.271)	<0.001	–2.028	(0.211)	<0.001
Social function	1.217	(0.409)	0.003	0.993	(0.343)	0.004	1.281	(0.258)	<0.001	0.498	(0.200)	0.013
Repetitive behaviour	0.333	(1.072)	0.756	–0.374	(0.945)	0.693	1.205	(0.678)	0.075	0.825	(0.557)	0.139
Unacceptable social behaviour	0.835	(0.687)	0.224	–0.808	(0.588)	0.169	–0.333	(0.463)	0.472	–0.436	0370)	0.238
Community-level variables
Child psychiatrist nearby	–0.351	(0.739)	0.635	–0.362	(0.651)	0.578	0.122	(0.543)	0.823	0.899	(0.402)	0.025
% College	–0.448	(0.541)	0.407	–0.623	(0.451)	0.167	–0.028	(0.378)	0.940	0.211	(0.261)	0.419
Logged median property value	0.733	(0.526)	0.163	0.533	(0.442)	0.228	0.024	(0.366)	0.947	–0.119	(0.269)	0.658
% In poverty	0.383	(0.330)	0.246	0.389	(0.288)	0.177	–0.139	(0.257)	0.588	–0.426	(0.236)	0.071
Lagged √autism rate	0.755	(0.379)	0.046	0.600	(0.331)	0.070	0.392	(0.289)	0.175	–0.049	(0.225)	0.829
Individuals	1987			2026			2131			1859
Clusters	725			763			735			746