Passage Summary: The author argues that because most adults with migraines were depressed as kids, a depressed kid will probably grow up to have migraines.

Conclusion: A child prone to depression is likely to suffer migraines as an adult.

Reasoning: Most adults who suffer from migraines were depressed as children.

Analysis: This argument commits a classic 'mistaken reversal' of probability. Just because most people in group B (migraine sufferers) started in group A (depressed children), it doesn't mean most people in group A will end up in group B. It’s like saying most professional basketball players are tall, so most tall children will grow up to be professional basketball players—a lovely thought for the tall kids, but statistically quite a stretch. Look for an answer choice that flips a correlation in this exact same way.