Can big breasts cause herniated disks?

Unlikely: Extremely large breasts can result in upper back pain. This is usually muscular in nature and can be very painful. Utilizing proper bra support may be helpful along with exercises to strengthen the back muscles. Breast reduction surgery had been shown to be very beneficial. I am unaware of any controlled studies that attribute disc herniations to breast size.

Probably not: Large breasts can cause symptoms of cervicalgia or muscular type neck symptoms to the point that breast reduction surgery has been done successfully to treat this type of neck symptomatology