2018考研英语长难句分析指导（三十八）

Dependence is marked first by an increased tolerance, with more and more of the substance required to produce the desired effect, and then by the appearance of unpleasant withdrawal symptoms when the substance is discontinued.

结构分析：句子主干是Dependence is marked first by…, with…, and then by…。with引导的是伴随结构作状语，修饰的是整个第一分句描述的状态。and引导的分句省略了谓语动词marked ，所以该分句并不隶属于第一分句，而是与之并列的结构，when引导的是第二个分句的时间状语从句。

译文：依赖最初表现为忍耐力增强，用量越来越大才能达到预期效果，一旦停用就会产生不舒服的症状。