NEW YORK (MainStreet)—You trust your financial advisor, but they're not your priest or rabbi, right? It's an office, not a confessional. Some things are not meant to be shared.

That's apparently the feeling of a significant number of investors, nearly one-third (29%) of which admit they haven't told their financial advisors about everything that could affect their finances.

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Securian Financial Group surveyed 720 consumers who work with financial advisors and more than half (52%) of those who withhold information say the information is simply too personal to share. Many of the survey respondents (45%) think the information falls into the "it's none of your business" category, saying the secrets are outside the scope of money matters and don't need to be shared. One fifth say their secrets are too embarrassing to reveal.

"They may not realize it, but personal matters can profoundly affect a family's financial stability," says Michelle Hall, a market research at Securian. "Health and marital difficulties rank high among the critical subjects clients do not discuss with their advisors." More than one-fourth carry debt their advisors don't know about.

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And the less-than-forthcoming clients are squarely in the target demographic advisors seek most. Nearly one-third are pre-retirees and retirees. Two-thirds are 40 and older. One-fifth are affluent, with $150,000 or more in annual household income, or mass affluent, with $100,000 to $149,000 of yearly income. Among those who are employed, two-thirds are in professional or managerial careers.

But the reluctance to reveal all may be due to more than modesty or shame. Clients just might not want to hear the advice that would be provided if their advisor were fully informed. When asked what changes their all-knowing advisors would likely recommend, half (50%) said increase savings or reduce spending. One-fourth (25%) said their advisors would want to create new financial plans.

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While keeping secrets, nearly half (48%) of all of the respondents say trust is the most important factor of their advisor relationships. And 43% say they do discuss other personal issues with their advisors. Of the 29% who withhold critical information, only 11% say it's because of a lack of trust.

"I make sure up front that they know I can only help them as much as they reveal to me," says Rich Preuss with The Healy Group in South Bend, Ind.

Joel Twedt, of Twedt Financial Services, has been an advisor for 34 years in Lake Mills, Iowa. When clients withhold information that could affect their financial plans, he doesn't pry.

"Some people are embarrassed to provide information so I don't ask," he says. "Once they get comfortable, it's amazing what they reveal. Quality advisors are counselors. It's not just about the clients' money: It's about their dreams, their fears, their families."

--Written by Hal M. Bundrick for MainStreet