Medical information is sensitive data, and the general rule about access to sensitive data is that it should be given on a need-to-know basis. The data belongs to you and you give access to it, so you need to determine if the other party has a need to know. I think your point is that the other party has a need to know because otherwise he might attribute your moodiness to his faults and you want to protect him from feeling unnecessary guilt. Is that why you want to disclose MI?