there is a box on amcas that you can check and then explain if you wish to be considered as disadvantaged. specific aspects of your experiences might come through in your secondaries, but it would be weird to say "and i'm disadvantaged" at that point - they will be looking for more specific things you have learned.
you can use your search function to find out more, ie:
This is what medical schools want to know if you claim you are disadvantaged:
1) Have you or members of your immediate family ever used federal or state assistance programs?
2) What was the income level of your family during the majority of your life from birth to age eighteen?
3) Did you have paid employment prior to age eighteen?
4) Were you required to contribute to the overall family income (as opposed to working primarily for your own discretionary spending money)?
5) How many people lived in your primary household during the majority of your life from birth to age eighteen?
6) How have you paid or did you pay for your post-secondary education? For each of the applicable options below, indicate the average percentage contribution towards your post-secondary education. The percentages entered should equal 100%.
7) Explain below why you believe you should be considered a disadvantaged applicant by your designated medical schools. The space available for your explanation is 1325 characters, or approximately ¼ page.
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The following definitions/questions may help you answer the questions regarding "disadvantaged":
Underserved: Do you believe, based on your own experiences or the experiences of family and friends, that the area in which you grew up was adequately served by the available health care professionals? Were there enough physicians, nurses, hospitals, clinics, and other health care service providers?
Immediate Family: The Federal Government broadly defines "immediate family" as "spouse, parent, child, sibling, mother or father-in-law, son or daughter-in-law, or sister or brother-in-law, including step and adoptive relationships."
State and Federal Assistance Programs: These programs are specifically defined as "Means-Tested Programs" under which the individual, family, or household income and assets must be below specified thresholds. The sponsoring agencies then provide cash and non-cash assistance to eligible individuals, families, or households. Such programs include welfare benefit programs (federal, state, and local) Aid to Families with Dependent Children (AFDC or ADC); unemployment compensation; General Assistance (GA); food stamps; Supplemental Security Income (SSI); Medicaid; housing assistance; or other federal, state, or local financial assistance programs.
