Adding to a woman’s increased dose of stress chemicals are her increased opportunities for stress

参考译文：女性承受压力的机会增多，使得产生压力的化学物质也随之增加。

以上为倒装结构，还原陈述语序后为下面句子

Her increased opportunities for stress are adding to a woman's increased dose of stress chemical.

以上句子语法结构分析如下

Her increased opportunities for stress【主语】// are adding to 【谓语动词】//a woman's increased dose of stress chemical【宾语】.

Her increased 【前置定语】// opportunities【主语】//  for stress【后置定语】// are adding to 【谓语动词】//a woman's increased dose of stress chemicals【宾语】.