COMPLICATE

[verb] [T] - to make (something) more difficult to deal with, do or understandThree of the dinner guests don't eat meat, two are on a diet and just to complicate matters/things, the sixth is allergic to milk.It will only complicate the situation/issue if we invite his old girlfriend as well.The rescue operation has been complicated by bad weather.The new rules have complicated the tax system even further.If something, esp. an illness, complicates another illness, it makes the other illness worse.His breathing problem has been complicated by a chest infection.