Child maltreatment has a range of effects on children which are dependent on the characteristics of the maltreatment (type, frequency, length, perpetrator) interacting with the characteristics of the child (age, personality, gender, developmental stage) and the protective factors present that could potentially mitigate the impact of the maltreatment. Some children are able to withstand and overcome the adversity of child maltreatment with relatively few lingering consequences. In other cases, the impact is physically or emotionally significant. Many of the effects can be long term and may not appear until the individual is well into adulthood.
The developing brain is shaped by experiences. When those experiences are inconsistent or threatening in nature, the brain anticipates those types of experiences and responds in accordance. In the case of maltreatment, if the child knows the perpetrator and, in particular if the perpetrator is a parent or primary caregiver, the injury to the child comes not only from the covert act of maltreatment but from the harm inflicted by loss of trust and security due to a dysfunctional and damaged interpersonal relationship. The child can learn to associate fear and distrust with the parent rather than comfort and safety. Very young infants and babies are particularly susceptible as their brains are laying down the foundations for future patterns of relationship building and learning. As a result, a baby whose caregiver consistently ignores her emotional needs eventually stops looking to her caregiver for comfort or emotional responsiveness. As she grows she will likely struggle to read social cues, build healthy relationships and understand her own emotions and feelings. She is more likely to lack the ability to parent and nurture her own child effectively.
The physical and emotional threat of danger created by child abuse (or by lack of basic resources and protections in the case of neglect) activates the body's involuntary fight, flight, or freeze response. This response focuses the brain and body on basic survival. Thought processes are restricted and the body is flooded with hormones to prepare for the burst of energy necessary to optimize survival. When activated repeatedly and with regularity, the constant dose of stress hormones produced by this response can overwhelm the child's system. Responses that were initially adaptive for a child's survival cannot be turned off. As a result, the child's brain can become extremely sensitized to the potential for danger. He or she may have a tendency to overreact to the level of threat, become hypervigilant or misread other's innocuous behavior as threatening. This state of heightened arousal often causes difficulty with focus, attention and maintenance of self-control which can impact school performance and social interactions. Conversely, the child can become so overwhelmed that his or her brain compensates through disassociation or detachment from the immediate reality and surroundings.
Child maltreatment can be a trauma producing experience for a child. Trauma is defined by the individual's reaction to an experience and not by the specific event(s). Therefore, whether maltreatment is traumatic is based on the reaction of the child in response to the characteristics of the maltreatment. A traumatic childhood experience is characterized by the following
- threat to the life or physical integrity of the child or of someone who is critically important to that child (for example a parent, sibling or close family member)
- an intense physical and emotional reaction which is overwhelming to the child
When experiences of child maltreatment produce a trauma reaction, they cause the child to experience traumatic stress. Traumatic stress is a persistent reaction to trauma that influences a child's ability to function and interact with others in their daily lives, even if the traumatic events have ended.
 If the trauma persists over time the stress can become toxic to the brain, triggering adverse effects on physical and emotional development, reshaping the brain architecture, influencing learning and behavior and impacting lifelong health. The likelihood of this type of reaction to traumatic stress increases if the trauma is chronic, consisting of multiple, ongoing, and sometimes varied, traumatic events such as those triggered by child abuse and neglect. Even more destructive is complex trauma where the chronic trauma of child maltreatment occurs at a very young age and is caused by caregivers who should be the source of protection and nurturance for the child.
Genetic research has revealed that the toxic stress resulting from child maltreatment can induce epigenetic changes or alter the way the child's brain directs genes to express themselves. Health factors such as the propensity or resistance to disease are biologically embedded in an individual's genetic code and can be switched on or off by this altered brain structure.
 Consequently, maltreatment that occurs in childhood can change an individual's biology in ways that have the potential to continue to affect health and well-being throughout adulthood.
The Adverse Childhood Experiences (ACE) Study is one of the most comprehensive research investigations linking child maltreatment and compromised health and well-being in adulthood. The original ACE study was conducted in San Diego the 1990's by Dr. Robert Anda from the Center for Disease Control and Prevention and Dr. Vincent Felitti of Kaiser Permanente.
 The ACE Study was the first large-scale study looking at short- and long-term impacts of childhood trauma.
According to Drs. Anda and Felitti, an ACE is a stressful or traumatic experience in childhood as a result of child abuse or household dysfunction. Drs. Anda and Felitti created a survey that simply asked an individual to indicate whether or not they had experienced abusive, neglectful or experiences of household dysfunction in childhood. Table 1 indicates the specific factors measured in their questionnaire. Anda and Felitti then calculated a score for each individual where an affirmative answer regarding that factor equaled one ACE and the total count of ACEs were summed to reach a number between 0 and 10. Each individual's ACE score was then compared to their health history. Among the 17,000 primarily middle-class, well-educated adults surveyed in California, ACEs were linked to an increased risk of numerous unhealthy behaviors, chronic disease, impaired mental health, and disability. Furthermore there is a dose response relationship between ACEs and health conditions; i.e. the more ACEs an individual has experienced, the more severely their health is likely to be compromised. ACEs have a long-term effect on the mind and body, increasing the likelihood of disease, speeding up the aging process, and making daily life less pleasurable and satisfying.
Table 1: Types of Adverse Childhood Experiences
Household Substance Abuse
Parent Treated Violently
Household Mental Illness
Incarcerated Household Member
*The adverse childhood experiences measured by Drs. Anda and Felitti are not an exhaustive list. There are numerous other types of childhood adversity. They can include one–time occurrences such as a natural disasters or the death of a parent. They can also be sustained over time such as ongoing poverty or racism.
Several years ago the Wisconsin Child Abuse and Neglect Prevention Board led efforts to incorporate ACE questions into Wisconsin's annual Behavioral Risk Factor Survey. Between 2011 and 2015 a total of 25,518 Wisconsinites responded to the ACE questions. The Wisconsin ACE study found the following:
ACEs are common in Wisconsin.
Approximately 3 out of every 5 Wisconsin adults have reported experiencing one or more ACES.
ACEs tend to cluster or occur together.
Of the Wisconsin adults who experienced one or more ACEs, almost 25% of that same group reported experiencing a total of four or more ACEs.
ACEs have a dose response relationship to numerous poor outcomes.
A dose-response relationship means the higher the number of ACEs, the more likely an individual will experience negative outcomes. For example higher ACEs scores are associated with lower income, lack of health insurance, less education, poor health, and reduced quality of life.
Higher ACE scores are associated with poorer physical health.
Individuals with higher ACE scores were found to have:
Higher incidence of engaging in health risk behavior such as smoking or lack of exercise.
Poorer general health such as obesity, frequent minor illness and daily aches and chronic health conditions.
Increased likelihood of suffering from major maladies such as cancer, arthritis, diabetes and asthma.
Higher ACE scores are associated with poorer mental health.
The higher the ACE score, the greater the incidence of depression, stress and difficulty with emotional regulation.