You are disabled and under 65 Will your pension amount be reduced by early withdrawal?

Social security benefits yes. For other pension plans you should get this information from the trustee of the plan.

If you are under the age of 59 1/2 and you do not meet the IRS rules for the disabled exception from the 10% early withdrawal penalty the taxable amount of the distribution during the year will be subject to the 10% early withdrawal penalty.