Some anticonvulsants have become popular for the treatment of mood disorders like bipolar disorder. Research indicates that the use of anticonvulsants may be responsible for the reduction of bone mineral density and may increase the risk of fractures.
The use of anticonvulsants may increase the risk of fracture by 1.2 to 2.4 times. Decreased bone mineral density can show up within five years or less of beginning the use of anticonvulsants.
"It appears that older post-menopausal women may be at greater risk for bone loss and fracture given lower baseline bone density, lower levels of physical activity, and decreased exposure to sunlight (which triggers vitamin D synthesis). It is clear, however, that healthy pre-menopausal women may also experience bone loss when treated with anticonvulsants."
Exposure to moderate sunlight, weight bearing exercise, and avoiding other drugs that may reduce bone mineral density are some measures that are recommended. Vitamin D may also increase bone mineral density.
http://www.womensmentalhealth.org/posts/anticonvulsants-and-bone-loss