Check words in documents
If your documents were actually lists of words, like your description said at one point, this would be way more efficient. But we can of course just make them, by using:

doc1 = "My sister likes to have sugar, but not my father.".split()
doc2 = "Doctors suggest that driving may cause increased stress.".split()


This has the problem that the punctuation gets in the way, so we need to remove it first, with one of the approaches from here (I chose the fastest one):

import string
doc1 = "My sister likes to have sugar, but not my father.".translate(None, string.punctuation).split()
doc2 = "Doctors suggest that driving may cause increased stress.".translate(None, string.punctuation).split()


Ok, now that they are lists, we make them into sets, so word in doc becomes \$\mathcal{O}(1)\$ instead of \$\mathcal{O}(n)\$:

documents = map(set, [doc1, doc2])

# DICTIONARY
dictionary = ["doctors", "sister", "like"]

for word in dictionary:
    for doc in documents:
        if word in doc:
            print "\n\n\nWord:",
            print word,
            print "in document:",
            print doc


This should speed this up considerable. The most speed-up will be gained if the document strings are quite long.

The output of this is now not really understandable anymore:

Word: sister in document: set(['sister', 'my', 'father', 'but', 'sugar', 'to', 'likes', 'have', 'not', 'My'])


We can get around that by carrying around both the set and the string. I also made the splitting into words a function and used a if __name__ == "__main__" guard to ensure this code is only run when calling it via e.g. python script.py, but not when doing from script import get_words.

import string

def get_words(text):
    return set(text.translate(None, string.punctuation).split())

if __name__ == "__main__":
    documents = ["My sister likes to have sugar, but not my father.",
                 "Doctors suggest that driving may cause increased stress."]

    words_in_documents = map(get_words, documents)

    for word in ["doctors", "sister", "like"]:
        for doc, words in zip(documents, words_in_documents):
            if word in words:
                print "\n\n\nWord: {} in document: {}".format(word, doc)