It depends on the relationships between the words and the clarity or lack of clarity in the combination: Your 'risky decision-making' is a noun phrase (object of 'associated with') and its meaning is 'a risky type of decision-making'; 'risky' modifies the noun, and the hyphen makes that clear. If it were to read 'risky-decision making', it would mean that the 'making' is only of risky decisions-- in other words, stressing the kind of decisions rather than the kind of decision-making. Let's look at a simpler case, though: 'He is a terrible tiger-trainer' -- he is no good at training tigers.
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