Does the First Spouse have security clearances?

Does the First Spouse often or always have security clearances so that the president can talk about what’s going on at work with his/her spouse? I’m watching The Event,and President Blair Underwood (I can’t remember the character’s name) keeps debating with his wife what he should do. She knows as much as the Vice President, the Director of the CIA, and a few other top officials – but certainly not the mass public. What about when it’s not a matter of national security, but still a secret – does the president share with his/her spouse then? What’s the policy on this?