Major depressionis one of the most commonclinicalproblemsseen by primary-carephysicians.The prevalenceis 5% to 10% in primary-careoutpatientsand 15% in medicallyill inpatients. Despite this high prevalence rate, depression is frequently not accurately diagnosed. Evidence suggests that misdiagnosis often occurs because patients with depression frequently focus preferentially on somatic complaint...

‎in this paper we give a characterization for all commutative‎ ‎rings with $1$ whose zero-divisor graphs are $c_4$-free.‎