谁能解释一下这个句型？

Prep遇到的一道题：

Some patients who do not respond to therapies for depression may simply have received inadequate treatment, having, for example, been prescribed a drug at a dosage too low to be effective or having been taken off a drug too soon.

划线部分这是个从句吧？照意思看它应该是修饰前面整句话（patients may have received inadequate treatment）？有这样的用法吗？但是“having been ...“又像是修饰patients...

请NN们赐教！

不是nn跟nn们探讨一下，我的理解是这里having是做动名词的形式，修饰前边那个句子，类似的用法是新东方里讲过的那种，逗号后边的修饰成分如果要表达前边整个一个句子，坚决不能用which和to do ，而要用一个名词或者是动名词形式

我觉得。。。应该不是修饰patients的，应该修饰离它最近的这个treatment。。

那么which在什么时候用？不是修饰非限制性定语从句，修饰前面的整个部分吗？

这个which我总是搞不懂

在网上查了一下，顺便重温了一下高中时学的那些什么定语呀，分词呀，完全忘了，呵呵

这句话应该是现在分词短语作状语，起补充说明作用。所以并不是很严格的修饰某个词或句子。但就像所有其它的现在分词短语作状语的情况一样，必须保持主谓一致。

起补充说明这个用法不是很常见，一般都是做时间状语“Walking slowly across the grass，he pointed the gun at the lion and fired”，结果状语“Her husband died ten years ago，leaving her with three children to look after”，伴随状语“He sat in the armchair，reading a newspaper.”等。

再来看这句话：

Some patients who do not respond to therapies for depression may simply have received inadequate treatment, having, for example, been prescribed a drug at a dosage too low to be effective or having been taken off a drug too soon

这么一看就觉得解释得通了。

 簡單來說,

having, for example, been prescribed a drug at a dosage too low to be effective or having been taken off a drug too soon

這一整句話可以換成for example, having been.....

所以就可以看到這一句話是用來解釋前面的may simply have received inadequate treatment

就是舉例的意思

不知道這樣說對不對~"~

請NN指教^^