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... strong possibility of jealousy. It can be very hard on anyone, even family members, to feel like they struggle with what comes easily to someone else.

It's not a pleasant topic, but, there is plenty to observe of people chiding the highly intelligent people.
One possible approach, when faced with an anecdote regarding the rise and fall of a gifted individual, may be to thank the person for sharing, express empathy for the person being mentioned, agree that you've heard of such difficulties... then share that there is a great support network for the gifted, including hoagies facebook page & Davidson public forums, free and available to all... adding that with the advice and resources available from such gifted support communities your family is hoping to avoid major setbacks. Gifted adults may also look toward the gifted support communities for resources for healing and finding a positive path.

In helping to spread the word about the existence of gifted support communities, a person may keep the conversation positive, and may help a struggling individual. This approach may also help reveal the intention behind the anecdote.