As previously mentioned, people who care for others informally can suffer from a condition known as caregiver stress. This usually manifests itself in angry episodes and cases of extreme fatigue. It is a type of burnout associated with both professional caregivers as well as those volunteering. Another sub-type is called wear-out. Some people will also refer to this sub-type as brown-out. Essentially, it occurs when someone sees too little by way of rewards for the effort they are putting in, so they quit in order to seek other opportunities. Frenetic burnout occurs when someone feels pressurised, so they work more and more, often creating greater stress as they do so. This can eventually lead to becoming burned out unless a managerial intervention is made by leadership. At the other end of the scale is a sub-type known as under-challenged burnout. This is basically when someone feels unrewarded because their workload is not challenging or interesting enough.