Many studies report an ethnic density effect whereby psychosis incidence among ethnic minority groups is higher in low co-ethnic density areas. It is unclear whether an equivalent density effect applies with other types of socioeconomic disadvantages.

We followed a population cohort of 2 million native Danes comprising all those born on 1st January 1965, or later, living in Denmark on their 15th birthday. Socioeconomic disadvantage, based on parents' circumstances at age 15 (low income, manual occupation, single parent and unemployed), was measured alongside neighbourhood prevalence of these indices.

Each indicator was associated with a higher incidence of non-affective psychosis which remained the same, or was slightly reduced, if neighbourhood levels of disadvantage were lower. For example, for individuals from a low-income background there was no difference in incidence for those living in areas where a low-income was least common [incidence rate ratio (IRR) 1.01; 95% confidence interval (CI) 0.93–1.10 v. those in the quintile where a low income was most common. Typically, differences associated with area-level disadvantage were the same whether or not cohort members had a disadvantaged background; for instance, for those from a manual occupation background, incidence was lower in the quintile where this was least v. most common (IRR 0.83; 95% CI 0.71–0.97), as it was for those from a non-manual background (IRR 0.77; 95% CI 0.67–0.87).

We found little evidence for group density effects in contrast to previous ethnic density studies. Further research is needed with equivalent investigations in other countries to see if similar patterns are observed.

许多研究报告了种族密度效应，即在低种族密度地区，少数民族的精神病发病率更高。尚不清楚等效密度效应是否适用于其他类型的社会经济劣势。

我们追踪了 200 万丹麦本土人的人口队列，包括所有出生于 1965 年 1 月 1 日或之后、在 15 岁生日时居住在丹麦的人。根据父母在 15 岁时的情况（低收入、体力劳动、单亲和失业），社会经济劣势与这些指数的邻里普遍性一起衡量。

每个指标都与较高的非情感性精神病发生率相关，如果邻里的劣势水平较低，则非情感性精神病的发生率保持不变或略有降低。例如，对于来自低收入背景的个人而言，与生活在低收入最不常见地区的人相比，发病率没有差异 [发病率比 (IRR) 1.01；95% 置信区间 (CI) 0.93–1.10与低收入最常见的五分位数相比。通常，无论队列成员是否具有弱势背景，与地区级劣势相关的差异都是相同的；例如，对于那些来自体力劳动背景的人来说，发病率在最低v 的五分位数中较低。最常见（IRR 0.83；95% CI 0.71-0.97），因为它是来自非手动背景的人（IRR 0.77；95% CI 0.67-0.87）。

与之前的种族密度研究相比，我们几乎没有发现群体密度效应的证据。需要通过在其他国家/地区进行同等调查来进一步研究，看看是否观察到类似的模式。