the core symptoms of adhd are inattention , hyperactivity , and impulsivity . in most descriptions of adhd in the 1980s and the early 1990s , it seemed that hyperactivity had to be present in every case as a striking symptom , but with growing knowledge of adhd it became evident that not all patients - in particular girls - present hyperactivity . since 1994 , with the fourth edition of the diagnostic and statistical manual of mental disorders ( dsm iv ) three types of adhd have been differentiated : combined type ( 6 or more symptoms of hyperactivity / impulsivity as well as of inattention ) ; inattentive type ( 6 or more symptoms of inattention ) ; hyperactive / impulsive type ( 6 or more symptoms of hyperactivity / impulsivity ) . after puberty , hyperactivity often changes to inactivity ; therefore , adhd often is not accepted as a diagnosis in adults . adults with adhd seem to have a problem with willpower : activity can be overexerted , but if a task is not attractive to the person , this results in a lack of effort . or , inattention can change to hyperfocussing , when the person is attracted by a task . with adults , differing patterns of comorbidity and symptom heterogeneity pose new conceptual , diagnostic , and treatment challenges . while core symptoms are often overt problems in children , in adults subtler executive dysfunction appears . even though the growing consensus is that adhd is a disorder of executive functions ( ef ) , the details of the ef / adhd connection remain unclear and may be far more complex in adults .   in table i examples are given for the changes of the 18 dsm - iv symptoms from childhood to adulthood . the 6-question adult self - report scale -v1.1 ( asrs - v 1.1 ) screener ( http://www.hcp.med.harvard.edu/ncs/fpdir/adhd ) is a subset of the who 's 18-question adult self- report scale - v1.1 ( asrs - v1.1 ) symptom checklist . four or more checkmarks in the darkly shaded areas may indicate that the symptoms are consistent with adult adhd ( figure 1 ) . wender developed a set of characteristics to specify both childhood criteria and current adhd symptoms . he pointed out affective lability , which is not mentioned in dsm - iv , as a frequent symptom in adult adhd . the prevalence of adhd in children according to dsm - iv criteria varies from 2.4% to 19.8% . the largest follow - up study , which investigated 197 chinese children after 15 years , showed a rate of persistence of 70% : generally , the degree of prevalence ( 1 % to 6% in adults ) depends on the view of the reporter in the initial assessment . most instruments consist of some form of self - report , and in adulthood it is often not possible to ask information of parents or persons with a close relationship to the patient . patients with adhd are often not aware of their symptoms , or do not report the severity of symptoms . neurochemical , neurophysiological , and radiological attributes were noted , proving , in particular , abnormalities in the dopaminergic and noradrenergic system . genetic investigations showed increased evidence that genetic components were present in most cases of adhd , which is now seen as the psychiatric disease with the highest heritability . neuroimaging studies with magnetic resonance imaging ( mri ) , photon - emission tomography ( pet ) , and single photon - emission computed tomography ( spect ) suggest involvement of striatal structures in adhd . molecular genetic studies described an involvement of a polymorphism of the dopamine transporter ( dat ) 1 gene in adhd ( eg , a higher rate of homozygosity of the 10-repeat allele in the 3 ' untranslated region of exon 15 of the dat gene on chromosome 5p15.3 ) . with regard to the suspected striatal impairment in adhd and the known effect of methylphenidate on the dat mainly localized in this section of the brain , since the end of the 1990s dat has been investigated in patients with adhd . this is carried out by using radioactive marked ligands which are known to bind effectively with the dat system . a group of investigators from boston used altropane marked with iodine-123 ; our group from munich and philadelphia used the cocaine derivative trodat-1 marked with technetium 99 m . both studies showed a clearly higher availability of dat in the striatum of adult patients with adhd compared with the normal healthy controls . while dat availability was found to be raised to 17% in the investigations using trodat-1 compared with the control collective ( figure 2 ) , the group using altropane demonstrated a rise of 70% in 6 patients ; this percentage was reduced to around 30% in a larger group of 19 patients on continuation of the altropane study ( spencer t , personal communication ) . meanwhile , a rise in dat availability was also detected in the basal ganglia of children with adhd by means of an [ i ] n-(3-iodopropen-2-yl)-2-carbo - methoxy-3-(4-chlorphenyl ) tropane ( ipt)-spect investigation , following initial results with n--fluoropropyl-2 -carboxymethoxy-3 -{4-iodophenyl } tropane ( fp - cit ) . interestingly , a rise in the dat could not , be detected in a spect investigation with -cit26 ; this could be due to the extremely slow kinetics of -cit ( measurement 1 day after application ) or another specificity of this radiotracer , which also binds with serotonin transporters and possibly holds other substructures of dat compared with altropane , fp - cit , ipt , or trodat-1 . our own initial results revealed that the dat was raised not . only in the hyperactive - impulsive and combined type , but also in the inattentive type of adhd ( figure 3 ) . it , may be deduced from a neurochemical view that with an increase in dat , which transports dopamine back from the synaptic cleft , less dopamine is available in the synaptic cleft of dopamine - dependent neurons . the results obtained by our group showed not , only the impairment of dat but also reported for the first , time in vivo and intraindividually in patients with adhd , that impaired metabolism can be improved with methylphenidate : on administration of 5 mg 3 times daily it was seen that there was a clear reduction in dat availability in all patients after a period of 4 weeks ( figure 2 ) . with this very low dose , most of these patients demonstrated a lower concentration of dat than did the control group . in a study involving six children with adhd , an ipt - spect investigation confirmed a marked reduction in dat density under administration of methylphenidate . regarding normal healthy individuals , other authors were able to show evidence of a similar reduction in dat under methylphenidate in a pet investigation with [ c - ll ] cocaine . in conclusion , the spect investigations on dat confirmed the supposition that with adhd an impairment is present mainly in the dopaminergic system . our initial results show that , nonresponders to methylphenidate do not reveal raised dat in striatum prior to therapy , whereas the responders seem to have a high dat availability ( figure 4 ) . it should be noted , for possible diagnostic applications of spect , that the dat concentration decreases with increase of age and that nicotine may influence dat availability . the lowering of dat with increasing age may be an explanation for our observation , that most , adults need lower doses of methylphenidate compared with children and adolescents . nicotine seems to have a similar effect on the dat as do stimulants ( figure 3 ) . investigating potential reasons for the lower elevation in the trodat-1 study compared with the altropane study , we found a subgroup of patients with relatively little increase in dat despite severe clinical impairments ; further questioning of these patients revealed that all of them were cigarette smokers . comparison of 11 smoking nonmedicated patients with adhd with sex- and agematched nonsmoking drug - naive adults with adhd showed significantly higher dat density in the nonsmoking patients , despite higher adhd scores for the smokers . this finding suggests that nicotine may act , directly on dat in the same manner as stimulants . in a self - trial , dat availability was reduced by over 50% 5 hours after intake of 20 mg methylphenidate in a slow - release formulation ; wearing a nicotine skin patch , equaling 10 to 20 cigarettes daily , for 5 hours . in the same subject 3 months later , an effect similar to that of methylphenidate was seen ( figure 5 ) , confirming the view that the lowering of dat after use of nicotine is not a sign of a neurochemical adaptation associated with chronic exposure to nicotine . further evidence comes from the reevaluation of a woman with adhd , who was smoking 15 cigarettes per day at , the time of first investigation with trodat-1 , showing no remarkable elevation of dat ; 4 weeks of intake of 3x5 mg methylphenidate led to a marked reduction similar to the other patients in this group . one year later , the patient stopped the nicotine and methylphenidate intake ; 2 years after the first investigation she returned with increased complaints of adhd . at this time she underwent another trodat-1 spect scan , presenting with a 19% elevation compared with the first scan with nicotine and a 61 % elevation compared with the second scan with nicotine and methylphenidate ( figure 6 ) . this finding is in accordance with the opinion that , the effect , of nicotine on dat does not result , in a persistent , loss of dat . in this context , it is of interest that an investigation with [ i]-cit spect showed no altered striatal uptake in smokers versus controls , a potential parallel to the above mentioned findings of no dat elevation in adhd with this method . most patients need multimodal therapy : psychoeducation concerning the special aspects of adhd is essential . many patients have problems with their self - esteem due to a misunderstanding of the symptoms and a childhood with parents suffering from adhd - especially impulsivity - and they need additional psychotherapy . treatment with stimulants is the drug therapy of first choice and is approved in the usa for adults ( dmethylphenidate and amphetamines ) ; stimulants for adult adhd are as effective as in children . an investigation performed in the year 2000 in germany showed that only 0.024 of the adults registered in the public health system - that is 90% of the adult , population - was treated with methylphenidate in germany at , this time ( figure 7 ) . that is about one out of 40 000 and includes all kinds of treatments , including for narcolepsy and other psychiatric diseases . in the treatment , of adults with adhd we start with a daily dose of 5 mg , reaching 15 mg methylphenidate after 14 days of treatment . titration up to 40 mg follows , if the patient needs more than the initial end point of the 15 mg dose . but more than 70% of our patients did not tolerate doses above 30 mg without having marked side effects . with higher doses , they also described a state resembling the impairments they experienced before the treatment . most , of them had a good stabilization with a combination of methylphenidate in a dose up to 20 mg and additional antidepressants . with all patients when methylphenidate has no positive effect on depressive or other comorbid symptoms , we start an additional medication after 4 weeks of treatment . some patients do not tolerate methylphenidate well ; they feel more depressed after starting the methylphenidate medication , but they are not as inattentive as before the beginning of therapy ; in this situation we change from methylphenidate to amphetamines ; some patients have more benefits from this kind of stimulants acting in dual ways . when selecting the additional medication it , is important to regard the comorbid disorder . we experienced good clinical response with the following medication : depression : venlafaxine 18.75 - 150 mg / d depression combined with severe distraction : amisulpride 25 - 100 mg / d ocd : sertraline 50 - 100 mg / d borderline syndrome : venlafaxine 37.5 mg -150 mg / d slight autistic symptoms : fluoxetine 10 - 20 mg / d the use of tricyclic antidepressants is problematic , as the long - term effect is not as good as that of treatment with new antidepressants . this substance does not influence the dopamine in the striatum , but in the prefrontal cortex , where dopamine transport is mediated by norepinephrine transporter .
the persistence of attention deficit hyperactivity disorder ( adhd ) into adolescence and adulthood has now been accepted as a clinical entity . 
 the rate of prevalence among adults is assumed to be from 2% to 4% . with increasing age 
 , a symptom change has to be considered ; disturbance of attention becomes more prominent , whereas hyperactivity often diminishes or changes to inactivity . 
 neuroimaging studies show a high striatal dopamine transporter ( dat ) availability in most adults with adhd ; this can be reduced by stimulants . 
 nicotine seems to have a stimulant - like action on the dat . in most adults with adhd 
 , therapy has to be multimodal , combining psychotherapy and medication . 
 methylphenidate is the first - line drug in adult adhd ; further options are amphetamine and noradrenaline reuptake inhibitors . 
 nonresponders to methylphenidate seem to have no elevated dat availability prior to therapy . combination with other psychiatric disorders occurs frequently in adults with adhd ; in these patients additional pharmacological treatment with special regard to the comorbid disease is recommended .